Decreased insulin-mediated glucose uptake by skeletal muscle, which accounts for one-third of total body mass, plays a crucial role in the development of type 2 diabetes (T2D). However, the molecular mechanisms underlyin...Decreased insulin-mediated glucose uptake by skeletal muscle, which accounts for one-third of total body mass, plays a crucial role in the development of type 2 diabetes (T2D). However, the molecular mechanisms underlying this disorder remain poorly understood. In contrast to previous studies examining changes in phosphorylation of individual sites or global phosphoproteome profile of human skeletal muscle in response to insulin (euglycemic-hyperinsulinemic clamp test), the present study is the first to investigate changes in skeletal muscle signaling in response to a mixed meal normalized to body mass (a model of physiological postprandial response). Using mass spectrometry-based phosphoproteomics, postprandial changes across 4205 phosphorylation sites in 1208 proteins/protein groups were analyzed in healthy individuals ( = 8) and patients with obesity and T2D ( = 8) and key kinases associated with these changes were identified. Food intake altered phosphorylation levels of 70 sites in healthy individuals and 36 sites in patients. However, postprandial phosphorylation of canonical insulin cascade proteins was comparable between the groups, which might be attributed to significantly elevated postprandial blood insulin levels in the patients caused by a reduced insulin-dependent glucose uptake by tissues and a greater food intake compared to healthy individuals. Only healthy individuals exhibited changes in postprandial phosphorylation levels of several proteins regulating the translocation and/or exposure of GLUT4-containing vesicles (SRBS1, CIP4/2, ABI1, SVIL, CPZIP, PLEC, and COBL), suggesting that impaired insulin-dependent glucose uptake in skeletal muscle in patients with obesity and T2D is primarily due to impaired regulation of GLUT4-containing vesicles trafficking.
The PI3K/AKT signaling pathway is one of the most critical intracellular pathways, regulating cell proliferation, survival, and migration. Mutations in PI3K/AKT pathway components are frequently associated with progressi...The PI3K/AKT signaling pathway is one of the most critical intracellular pathways, regulating cell proliferation, survival, and migration. Mutations in PI3K/AKT pathway components are frequently associated with progression and metastasis of malignant tumors. The initial stage of metastasis is epithelial-mesenchymal transition (EMT), during which tumor cells acquire the migratory capacity. The data on the impact of PI3K/AKT driver mutations on tumor cell motility are contradictory. We investigated EMT and changes in the motility of breast epithelial cells carrying four driver mutations commonly identified in malignant tumors and affecting different components of the PI3K/AKT pathway. Analysis of cell motility, expression of EMT markers, and morphology of adherens junctions (AJs) revealed that all these mutations induced partial EMT, as E-cadherin expression was preserved in all studied cell lines and cells maintained AJs. Analysis of EMT types induced by different mutations revealed that the increased cell motility did not correlate with the degree of EMT progression toward the mesenchymal phenotype. The greatest increase in the cell migratory capacity was observed for cells carrying the H1047R mutation, which induced the most pronounced mesenchymal phenotype, as well as for cells, which retained the most epithelial phenotype. Our analysis showed that mutations indirectly affecting the MAPK/ERK pathway and promoting ERK activation have the greatest impact on EMT and cell motility.
Patients with coronary and cerebral atherosclerosis are characterized by increased levels of total serum calcium, ionized calcium, and phosphate, against a background of reduced levels of total serum protein and albumin....Patients with coronary and cerebral atherosclerosis are characterized by increased levels of total serum calcium, ionized calcium, and phosphate, against a background of reduced levels of total serum protein and albumin. Here we aimed to develop a rapid diagnostic assay for mineral homeostasis disorders, based on assessing capacity of the acidic plasma proteins to bind excess calcium and phosphate ions. Plasma from bony fish, amphibians, reptiles, birds, mice, and patients with myocardial infarction was incubated with excess concentrations of calcium and phosphate at 37°C for varying time periods. The following assay readouts were defined: (i) plasma optical density after supersaturation with calcium and phosphate ions, reflecting excessive formation of calciprotein particles (CPPs); and (ii) CPP concentration in plasma. CPPs were formed in all vertebrates. The most pronounced plasma calcification propensity was observed in the human and mouse plasma, suggesting an evolutionary significance of CPP formation as a mechanism for clearance of excess circulating calcium and phosphate ions in mammals. Among the 11 protocols of supersaturation with calcium and phosphate ions, stable increase in plasma optical density at 620 nm wavelength (normalized OD, a measure of plasma calcification propensity) was achieved by adding solutions of CaCl (+2 mmol/L, +50 µL), NaHPO·12HO (+2 mmol/L, +50 µL), and NaCl (+15.4 mmol/L, +20 µL) to plasma (80 µL). Increase in the normalized OD was consistently detected within 10 min from the reaction onset during incubation in a microplate shaker (37°C), with mild-to-moderate variability across the parallel or sequential measurements and between the different operators. These results support relevance of validating the developed diagnostic assay for assessing mineral homeostasis disorders in the expanded cohorts of patients with myocardial infarction and ischemic stroke.
Schizophrenia is a severe mental disorder whose molecular mechanisms remain poorly understood. Investigating brain-derived neurotrophic factor (BDNF)-dependent signaling pathways and their contribution to schizophrenia p...Schizophrenia is a severe mental disorder whose molecular mechanisms remain poorly understood. Investigating brain-derived neurotrophic factor (BDNF)-dependent signaling pathways and their contribution to schizophrenia pathogenesis is a promising research direction in schizophrenia research. BDNF activates multiple intracellular cascades, among which the MAPK/ERK pathway plays a central role. In this study, expression levels of key regulatory proteins of the MAPK/ERK signaling pathway (ERK1/2, STAT3, STAT5, NF-κB, IGF1R, IRS1, IR, TSC2, and CREB1) were examined in lysates of peripheral blood mononuclear cells (PBMCs) from schizophrenia patients using multiplex analysis. The study group included 58 patients diagnosed with schizophrenia (F20); the control group included 60 healthy individuals. The results revealed significantly increased expression of ERK1/2 and STAT3, along with decreased NF-κB levels, in PBMCs from schizophrenia patients compared to controls. Moreover, patients with leading positive symptoms exhibited elevated expression of CREB1 and ERK1/2. These findings suggest that dysregulation of the MAPK/ERK signaling may play a significant role in the pathogenesis schizophrenia. BDNF-dependent signaling pathways may therefore represent promising targets for diagnostics and therapy of this disorder.
Hepatitis B virus (HBV) infects human hepatocytes, causing acute or chronic liver infection. Chronic HBV infection leads to progressive liver damage, potentially resulting in cirrhosis or hepatocellular carcinoma. One pr...Hepatitis B virus (HBV) infects human hepatocytes, causing acute or chronic liver infection. Chronic HBV infection leads to progressive liver damage, potentially resulting in cirrhosis or hepatocellular carcinoma. One promising antiviral strategy involves activating cytidine deaminases of the APOBEC/AID family, which could induce mutational degradation of HBV. Using a CRISPRa-based transcriptional activation system with modified sgRNAs, we investigated antiviral and oncogenic effects of the activating genes encoding APOBEC3C, APOBEC3D, and APOBEC3H.
Everolimus, an mTORC1 inhibitor, may also affect proteasome activity in a manner similar to bortezomib, necessitating further investigation. In this study, we employed ultrafast expression proteomics in combination with...Everolimus, an mTORC1 inhibitor, may also affect proteasome activity in a manner similar to bortezomib, necessitating further investigation. In this study, we employed ultrafast expression proteomics in combination with cell viability and proteasome activity assays to identify potential secondary targets of everolimus and to obtain a more comprehensive understanding of its mechanism of action across the proteomes of multiple cancer cell lines. The results were compared with those obtained for bortezomib and lonidamine, which were used as positive and negative controls for proteasome inhibition, respectively. Our findings reveal that everolimus inhibits 20S proteasome in lung (A549) and colon (HCT116) cancer cells, while having no detectable effect in breast cancer cells (MCF-7). An model of everolimus interaction with 20S proteasome was built suggesting an allosteric mechanism of inhibition.
Mitochondria are semi-autonomous, multifunctional organelles that supply cells with energy. They are highly dynamic structures, capable of moving, fusing, dividing, and forming branched networks. The number, density, and...Mitochondria are semi-autonomous, multifunctional organelles that supply cells with energy. They are highly dynamic structures, capable of moving, fusing, dividing, and forming branched networks. The number, density, and complexity of mitochondrial network are unique to each cell type and reflect cellular demands for ATP and other mitochondria-dependent metabolites. Mitochondrial dysfunction is a hallmark of many neurodegenerative diseases; however, the relationships between neurodegeneration and mitochondrial morphogenesis, intracellular localization, and dynamics remain incompletely understood. Interpretation and comparison of published data are complicated by the diversity of analytical approaches used to study mitochondrial behavior. In this research, we investigated the effects of a pathogenic mutation in the huntingtin protein (HTT), which causes Huntington's disease (HD), on mitochondrial morphology and motility, with particular emphasis on associated disruptions in the cytoskeletal organization. We performed a systematic evaluation of automated mitochondrial analysis tools and selected , , and as the optimal platforms for quantitative assessment of the effects of mutant HTT (mHTT) on the mitochondrial morphology, motility, and interaction with cytoskeletal components and identification of specific disruptions directly related to HD pathogenesis. Our analysis revealed that mitochondria in mHTT-expressing cells are significantly shorter, more branched, and less motile than in control cells. Moreover, their interactions with microtubules and vimentin intermediate filaments are markedly altered. Together, these findings establish a link between HD and specific defects in the mitochondrial network, thus contributing to understanding cellular mechanisms of HD development, and suggest that mHTT disrupts the interaction of mitochondria with cytoskeletal components responsible for their movement and distribution in the cell, thereby negatively affecting mitochondrial motility and morphology.
Air pollution remains a major environmental challenge, largely driven by urban dust composed of suspended solid particles of diverse origins and chemical compositions. Particulate matter (PM) and ultrafine urban dust nan...Air pollution remains a major environmental challenge, largely driven by urban dust composed of suspended solid particles of diverse origins and chemical compositions. Particulate matter (PM) and ultrafine urban dust nanoparticles (NPs), with diameters smaller than 2.5 μm and 100 nm, respectively, pose a particular threat to human health. In this study, we present the first evidence that NPs induce pro-inflammatory activation of human bronchial epithelial cells. Exposure to non-cytotoxic concentrations of NPs led to a significant increase in the mRNA levels of pro-inflammatory markers IL-8, IL-1β, IL-6, and ICAM-1, accompanied by increased secretion of the cytokines IL-8 and IL-6. Heat treatment of NPs, which removed their organic components, completely abolished their ability to stimulate cytokine secretion. NP-induced upregulation of pro-inflammatory gene expression depended on both surface-adsorbed organic compounds and inorganic particle constituents.
β-Amyloid peptides (Aβ), which play a crucial role in the pathogenesis of Alzheimer's disease by forming toxic oligomeric species, are known to affect mitochondrial function. In this study, luciferin-luciferase assay was...β-Amyloid peptides (Aβ), which play a crucial role in the pathogenesis of Alzheimer's disease by forming toxic oligomeric species, are known to affect mitochondrial function. In this study, luciferin-luciferase assay was used to assess changes in ATP production by mitochondria isolated from human neuroblastoma SH-SY5Y cells cultured in the presence of monomeric Aβ at a nanomolar concentration. ATP synthesis rates were measured in the presence of substrates specific for respiratory chain complexes I, II, and IV alongside inhibitors targeting the other complexes. Aβ significantly reduced both the rate of ATP generation and amount of ATP synthesized by mitochondria. This effect of Aβ on ATP synthesis did not result from a direct influence on the respiratory chain complexes I, II, and IV. Our findings provide insights into possible causes of mitochondrial dysfunction in neurons in Alzheimer's disease.
Ecological adaptations of a species can be shaped by its repertoire of gene variants. The black garden ant shows high level of duplication. In contrast to its congener, the jet ant , it exhibits tolerance toward fungus...Ecological adaptations of a species can be shaped by its repertoire of gene variants. The black garden ant shows high level of duplication. In contrast to its congener, the jet ant , it exhibits tolerance toward fungus-infected aphids. In these two species, we compared expression of a subset of genes, potentially involved in mycotoxin metabolism. No significant differences in expression were found. Similarly to , the jet ant has six copies of these genes, grouping pairwise on the phylogenetic tree with their counterparts. Beyond the gene subset targeted in the expression study, we found multiple genes in the genomes of , , and - fewer by a third - in the outgroup , suggesting amplification as an ancestral trait of the genus Lasius or a more basal clade.
Hydrophobic weakly basic drugs, such as doxorubicin and sunitinib, are currently key components of cancer chemotherapy. It has been shown that several of these compounds induce increase in the total lysosomal volume in t...Hydrophobic weakly basic drugs, such as doxorubicin and sunitinib, are currently key components of cancer chemotherapy. It has been shown that several of these compounds induce increase in the total lysosomal volume in tumor cells. Moreover, hypoxia, a hallmark of solid tumors , promotes chemoresistance by sequestering doxorubicin within lysosomes. To enhance efficacy of chemotherapy, various strategies have been proposed, including those aimed at lysosome destabilization. Inhibition of autophagy is widely recognized as a means to reduce chemoresistance. However, it remains unclear whether doxorubicin itself directly influences lysosomal physiology. In the present study, using the human colorectal carcinoma cell line HCT116, we demonstrate that doxorubicin accumulates substantially in lysosomes even under normoxic conditions. Under normoxia, doxorubicin induces a marked increase in the total lysosomal volume, whereas this effect is weaker under hypoxia. Co-treatment with doxorubicin and chloroquine, a well-established lysosomotropic agent, results in the increased lysosomal volume under both normoxic and hypoxic conditions. Notably, under normoxia, doxorubicin activates TFEB (Transcription Factor EB), a master regulator of lysosomal biogenesis, which likely accounts for the observed expansion of the lysosomal compartment. Furthermore, the lysosomes retain their functional degradative activity in the presence of doxorubicin. A similar effect, lysosomal volume expansion and enhanced degradative capacity in response to doxorubicin, was also observed in the human fibrosarcoma cell line HT1080. In summary, this study provides the first evidence that doxorubicin directly modulates lysosomal parameters in the tumor cell lines under varying oxygen concentrations.
Biochemistry
· 2026 Apr · PMID 41837767
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Bioorganic chemists are inspired by natural biopolymers to design peptidomimetic oligomers that can exhibit sequence-structure-function relationships. Biomimetic polymers can be synthesized to incorporate a specific sequ...Bioorganic chemists are inspired by natural biopolymers to design peptidomimetic oligomers that can exhibit sequence-structure-function relationships. Biomimetic polymers can be synthesized to incorporate a specific sequence of nonbiological monomer units using a variety of iterative solution-phase or solid-phase reaction schemes. These protocols generally provide access to a vast diversity of oligomeric compounds but are limited with respect to their ability to attain protein-like chain lengths. This constraint can preclude access to sequence-defined synthetic macromolecules with sufficient sizes required to exhibit tertiary structure and other protein-mimetic attributes. In contrast, peptide chemists have overcome this limitation by developing convergent synthetic methods, such as native chemical ligation, to join individual, smaller peptide chains together to make larger peptides or full proteins. A similar convergent approach is needed to establish efficient synthetic routes to non-natural sequence-defined macromolecules. Herein, we adapt the peptide native chemical ligation method to peptoid oligomers, demonstrating how short chains can be conjoined to create sequence-defined peptoid macromolecules. Nanosheet-forming peptoid polymers with distinct surface loop display domains were generated by sequential ligation of several discrete fragments. This method provides a reliable convergent ligation route for sequence-defined polypeptoids that results in a native amide bond joining the fragments. We envision that this strategy will be useful in synthesizing peptoid-based proteomimetics that incorporate diverse chemical features.
Rice AJ, Xue Y, Liu A
… +4 more, Ramesh S, Ashiru OA, Sofela SO, Mitchell DA
Biochemistry
· 2026 Apr · PMID 41818325
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The ribosome is an intensively studied machine responsible for protein synthesis. Recent high-resolution structures of the ribosome unexpectedly revealed a thioamide on the large subunit protein uL16. This unusual and e...The ribosome is an intensively studied machine responsible for protein synthesis. Recent high-resolution structures of the ribosome unexpectedly revealed a thioamide on the large subunit protein uL16. This unusual and easily overlooked modification replaces oxygen with sulfur in the peptide backbone, and here, the modification is proximal to the peptidyl transferase center (PTC). The responsible enzyme has remained unidentified, although methanogenic YcaO enzymes are known to catalyze thioamidation of methyl-coenzyme M reductase. Here, we use several approaches to assign YcaO as the enzyme responsible for uL16 thioamidation. We began by individually predicting the structures of all proteins complexed with YcaO, revealing that uL16 was the only protein forming a high-confidence, catalytically competent interaction. Furthermore, we performed mutational analysis of the YcaO-uL16 binding interface, revealing an extensive, electrostatically complementary surface atypical of characterized YcaO enzymes. In log-phase , we observed a complex, nonlinear growth relationship between thioamidation and β-hydroxylation of uL16-Arg81, a neighboring PTC modification. Beyond , bioinformatics surveys predict that several thousand Pseudomonadota organisms will equivalently perform uL16 thioamidation. This prediction was validated for two Gram-negative human pathogens, and . Overall, this work has elucidated the enzyme responsible for uL16 thioamidation and demonstrated that this unusual modification is widespread in Pseudomonadota. Further, we have laid a critical foundation for understanding both the mechanism by which this modification is formed and its functional consequences. The approach leveraged here could also find broader use in identifying gene-encoded substrates for enzymes.
NMR spectroscopy is the most important technique for understanding the structure of peptides and proteins in solution. Contemporary publications in the interpretation of NMR spectra of peptides and proteins generally foc...NMR spectroscopy is the most important technique for understanding the structure of peptides and proteins in solution. Contemporary publications in the interpretation of NMR spectra of peptides and proteins generally focus on advanced techniques and complex spectra, with a lack of simple spectra and guides available for beginning students. A data set of H NMR spectra was generated from a series of simple peptides that include all canonical amino acids () [Ac-(S/pS)-NH, Ac-(T/pT)-NH, and Ac-PPGY-NH; pS = phosphoserine, pT = phosphothreonine]. The characterization of each peptide includes 1-D and TOCSY spectra, with both raw and processed data available. The spectra can be used for instructional applications, including analysis of regions of the spectra (e.g., amide, aromatic, Hα, and aliphatic); identification of spin systems and residue assignment via TOCSY spectra; analysis of conformational features including amide H chemical shift dispersion and changes due to hydrogen bonding or post-translational modifications; the coupling constant that reports on the ϕ torsion angle and on order versus disorder at a residue; conformational preferences at Hα via chemical shift index analysis; understanding of diastereotopic hydrogens; dynamic processes, including hydrogen exchange; and identification of proline - isomerism. In addition, for a limited number of peptides, NOESY spectra are included to allow sequential resonance assignment and for assignment of versus proline conformations. Spectra from closely related peptides allow the analysis of the relative effects of single amino acid changes. The paper is written to be directly accessible to students in research laboratories or in the classroom as a tutorial guide.
Chernitsky-Hamd D, Roy R, Schemm J
… +4 more, Schall A, Petros M, Willems A, Roepe PD
Biochemistry
· 2026 Apr · PMID 41810826
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The recently elucidated atomic resolution cryo-EM structure of the 7G8 isoform of chloroquine resistance transporter (PfCRT) suggests two pairs of proximal cysteine residues within the loop 7 (L7) domain. We wondered wh...The recently elucidated atomic resolution cryo-EM structure of the 7G8 isoform of chloroquine resistance transporter (PfCRT) suggests two pairs of proximal cysteine residues within the loop 7 (L7) domain. We wondered whether these might provide a redox active switch that might then regulate PfCRT function. Using site-specific mutagenesis, maleimide labeling, redox buffering, and chloroquine transport measurements, as well as molecular dynamics (MD) calculations, we probe the relative importance of all Dd2 PfCRT isoform C as well as their HS SH to S-S interconversion vs CQ transport function. Results show that CQ transport by PfCRT is regulated by the redox potential. We propose that disulfide bonds form at both the C289/C312 and C301/C309 pairs of Dd2 PfCRT and that these dynamic S-S bonds are required for full PfCRT CQ transport activity. Mutagenesis of all Dd2 PfCRT C to S or A reveals that no other C is functionally obligate but identifies C101, C139, C171, and C328 as involved in modulating CQ transport. Since two of the L7 C (C309 - C312) are within a CXXC motif (with X = D) that in theory can signify a metal binding site, we also model divalent metal ion binding using Metal3D and AlphaFold 3 and find that divalent metal may coordinate to C elsewhere in the protein but likely not to this CXXC motif. MD calculations done with 10 ns or 1 μs trajectories suggest large conformational changes in L7 near the initial drug binding site upon SH HS to S-S interconversion. Together, the data yield a model for how L7 disposed to the redox active digestive vacuole (DV) of the intraerythrocytic malarial parasite regulates PfCRT access to DV-disposed CQ.
Biochemistry
· 2026 Apr · PMID 41810515
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Cell-penetrating peptides (CPPs) are powerful tools for delivering membrane-impermeable biomolecules into eukaryotic cells, with broad applications ranging from therapeutics to biopesticides. However, conventional linear...Cell-penetrating peptides (CPPs) are powerful tools for delivering membrane-impermeable biomolecules into eukaryotic cells, with broad applications ranging from therapeutics to biopesticides. However, conventional linear CPPs typically require a high density of positive charges (at least +6) to function, often resulting in dose-limiting toxicity and off-target effects. Reducing this charge without sacrificing delivery efficiency remains a significant challenge. In this study, we performed a structure-activity relationship (SAR) analysis and medicinal chemistry optimization of the bismuth-mediated bicyclic CPP, BCP16. This campaign led to the discovery of BCP16e, a potent analog that carries only a +2 charge at physiological pH. Compared to its parent molecule, BCP16e exhibits significantly higher cytosolic entry efficiency, similar proteolytic stability, and a superior safety profile. Our findings demonstrate that high cationic charge is not a prerequisite for efficient translocation, providing a framework for the design of minimally charged, high-efficiency vehicles for intracellular delivery.
Assembly line polyketide synthases (PKSs) possess multimodular architectures in which each module harbors the requisite protein domains to catalyze a single round of polyketide chain elongation and postelongation modific...Assembly line polyketide synthases (PKSs) possess multimodular architectures in which each module harbors the requisite protein domains to catalyze a single round of polyketide chain elongation and postelongation modifications. Exceptions to this paradigm are modules that catalyze multiple elongation cycles, a phenomenon referred to as "programmed iteration". The molecular mechanism that allows PKS modules to iterate remains poorly understood. For example, Module 5 of the nocardiosis-associated polyketide (NOCAP) synthase catalyzes three elongation cycles during the biosynthesis of its undecaketide product, although in the absence of downstream modules, it has been shown to catalyze five elongation cycles. To understand the context-dependent control of its iterative capacity, we combined analysis of purified Module 5 of the NOCAP synthase with studies in . Our findings reveal that, while the ability to iterate is an inherent property of Module 5, protein-protein interactions with its downstream module (Module 6) are key determinants of the number of elongation cycles catalyzed by Module 5 within the context of the complete assembly line. We also show that the intrinsic ability of Module 5 to iterate can be strongly influenced by the identity of its substrate. Our findings highlight the potential of Module 5 of the NOCAP synthase to reveal fundamentally new insights into the mechanistic differences between iterative and assembly line PKSs.
Microsomal cytochromes P450 (CYPs) require electrons transferred from NADPH by cytochrome P450 reductase (CPR) to support O reduction and substrate oxidation. The CPR catalytic domain is tethered by a linker to an N-term...Microsomal cytochromes P450 (CYPs) require electrons transferred from NADPH by cytochrome P450 reductase (CPR) to support O reduction and substrate oxidation. The CPR catalytic domain is tethered by a linker to an N-terminal transmembrane domain, both of which are required to support CYP catalysis. However, details of the interactions of the tether and catalytic domains with the membrane surface are poorly understood. Herein, we describe the assembly, characterization, and interrogation of the structures of an ancestral CPR embedded in lipoprotein nanodiscs (NDs) composed of defined and microsomal lipids. No significant differences in the rates of NADPH oxidation between the NDs and detergent-solubilized CPR were observed; however, there were differences in the rates of cytochrome reduction. Using multicontrast small angle neutron scattering (SANS) and a grid-based molecular dynamics strategy to refine structures to density maps, it was determined that CPR-NDs assume a more compact solution structure than predicted by unrestrained molecular dynamics simulations. The tether domain lines the membrane surface, and the catalytic domain is positioned at the ND edge. To the extent that the SANS-based structure is representative of CPR-NDs with varying lipid composition, the interactions of the catalytic domain and scaffold protein likely interfere with cytochrome interactions, thereby resulting in varying rates of reduction. These studies report the first experimentally grounded structure of membrane embedded CPR and demonstrate that interactions between embedded and ND scaffold proteins cannot be neglected. This strategy is expected to contribute to the repertoire of methods to probe membrane protein-lipid interactions.
Biochemistry
· 2026 Mar · PMID 41790433
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Multiple classes of ribosomally synthesized and post-translationally modified peptides (RiPPs) are chemically modified with an enigmatic functional group, the aspartimide. This modification occurs via the action of an en...Multiple classes of ribosomally synthesized and post-translationally modified peptides (RiPPs) are chemically modified with an enigmatic functional group, the aspartimide. This modification occurs via the action of an enzyme related to the protein repair catalyst protein isoaspartyl methyltransferase (PIMT). Contrary to canonical PIMTs which methylate isoaspartate residues within a protein, RiPP-associated PIMTs directly methylate specific Asp residues within the RiPP substrate, resulting in the formation of an aspartimide. The biochemical details of aspartimidylation in three RiPP classes, lanthipeptides, lasso peptides, and graspetides, are described herein. The discovery of a new class of RiPPs, the imiditides or type I pamtides, with aspartimide as the class-defining post-translational modification, is also described. Finally, knowledge gaps as well as suggestions for future research are discussed.
The rapid emergence of multidrug-resistant (MDR) bacteria threatens the effectiveness of existing antibiotics and has created an urgent need for agents with novel mechanisms of action. Calcium-dependent antibiotics (CDAs...The rapid emergence of multidrug-resistant (MDR) bacteria threatens the effectiveness of existing antibiotics and has created an urgent need for agents with novel mechanisms of action. Calcium-dependent antibiotics (CDAs), a structurally diverse group of nonribosomal cyclic lipopeptides, have gained attention for their potent activity against Gram-positive pathogens, including strains resistant to conventional therapies. Their hallmark feature is Ca-mediated activation: the calcium ion binding to the lipopeptide enables selective interactions with bacterial lipids or cell-wall precursors. This review examines the relationship between CDA structure, Ca coordination, mechanistic diversity, and biological activity. Together, these features position CDAs as promising templates for next-generation therapeutics to combat the escalating MDR crisis.