Journal of Molecular Biology最新文献

{"title":"Insights into the A-C Mismatch Conformational Ensemble in Duplex DNA and its Role in Genetic Processes through a Structure-based Review","authors":"","doi":"10.1016/j.jmb.2024.168710","DOIUrl":"10.1016/j.jmb.2024.168710","url":null,"abstract":"<div><p>Knowing the conformational ensembles formed by mismatches is crucial for understanding how they are generated and repaired and how they contribute to genomic instability. Here, we review structural and energetic studies of the A-C mismatch in duplex DNA and use the information to identify critical conformational states in its ensemble and their significance in genetic processes. In the 1970s, Topal and Fresco proposed the A-C wobble stabilized by two hydrogen bonds, one requiring protonation of adenine-N1. Subsequent NMR and X-ray crystallography studies showed that the protonated A-C wobble was in dynamic equilibrium with a neutral inverted wobble. The mismatch was shown to destabilize duplex DNA in a sequence- and pH-dependent manner by 2.4–3.8 kcal/mol and to have an apparent pKa ranging between 7.2 and 7.7. The A-C mismatch conformational repertoire expanded as structures were determined for damaged and protein-bound DNA. These structures included Watson-Crick-like conformations forming through tautomerization of the bases that drive replication errors, the reverse wobble forming through rotation of the entire nucleotide proposed to increase the fidelity of DNA replication, and the Hoogsteen base-pair forming through the flipping of the adenine base which explained the unusual specificity of DNA polymerases that bypass DNA damage. Thus, the A-C mismatch ensemble encompasses various conformational states that can be selectively stabilized in response to environmental changes such as pH shifts, intermolecular interactions, and chemical modifications, and these adaptations facilitate critical biological processes. This review also highlights the utility of existing 3D structures to build ensemble models for nucleic acid motifs.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141618899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spectroscopically Validated pH-dependent MSOX Movies Provide Detailed Mechanism of Copper Nitrite Reductases","authors":"","doi":"10.1016/j.jmb.2024.168706","DOIUrl":"10.1016/j.jmb.2024.168706","url":null,"abstract":"<div><p>Copper nitrite reductases (CuNiRs) exhibit a strong pH dependence of their catalytic activity. Structural movies can be obtained by serially recording multiple structures (frames) from the same spot of a crystal using the MSOX serial crystallography approach. This method has been combined with on-line single crystal optical spectroscopy to capture the pH-dependent structural changes that accompany during turnover of CuNiRs from two <em>Rhizobia</em> species. The structural movies, initiated by the redox activation of a type-1 copper site (T1Cu) <em>via</em> X-ray generated photoelectrons, have been obtained for the substrate-free and substrate-bound states at low (high enzymatic activity) and high (low enzymatic activity) pH. At low pH, formation of the product nitric oxide (NO) is complete at the catalytic type-2 copper site (T2Cu) after a dose of 3 MGy (frame 5) with full bleaching of the T1Cu ligand-to-metal charge transfer (LMCT) 455 nm band (S(σ)_Cys → T1Cu²⁺) which in itself indicates the electronic route of proton-coupled electron transfer (PCET) from T1Cu to T2Cu. In contrast at high pH, the changes in optical spectra are relatively small and the formation of NO is only observed in later frames (frame 15 in <em>Br^2D</em>NiR, 10 MGy), consistent with the loss of PCET required for catalysis. This is accompanied by decarboxylation of the catalytic Asp_CAT residue, with CO₂ trapped in the catalytic pocket.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022283624003152/pdfft?md5=6b7fe5e7cd5a1c41f3fbd91a48baf02b&pid=1-s2.0-S0022283624003152-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141603081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The RNA-binding Selectivity of the RGG/RG Motifs of hnRNP U is Abolished by Elements Within the C-terminal Intrinsically Disordered Region","authors":"","doi":"10.1016/j.jmb.2024.168702","DOIUrl":"10.1016/j.jmb.2024.168702","url":null,"abstract":"<div><p>The abundant nuclear protein hnRNP U interacts with a broad array of RNAs along with DNA and protein to regulate nuclear chromatin architecture. The RNA-binding activity is achieved via a disordered ∼100 residue C-terminal RNA-binding domain (RBD) containing two distinct RGG/RG motifs. Although the RNA-binding capabilities of RGG/RG motifs have been widely reported, less is known about hnRNP U’s RNA-binding selectivity. Furthermore, while it is well established that hnRNP U binds numerous nuclear RNAs, it remains unknown whether it selectively recognizes sequence or structural motifs in target RNAs. To address this question, we performed equilibrium binding assays using fluorescence anisotropy (FA) and electrophoretic mobility shift assays (EMSAs) to quantitatively assess the ability of human hnRNP U RBD to interact with segments of cellular RNAs identified from eCLIP data. These RNAs often, but not exclusively, contain poly-uridine or 5′-AGGGAG sequence motifs. Detailed binding analysis of several target RNAs reveal that the hnRNP U RBD binds RNA in a promiscuous manner with high affinity for a broad range of structured RNAs, but with little preference for any distinct sequence motif. In contrast, the isolated RGG/RG of hnRNP U motif exhibits a strong preference for G-quadruplexes, similar to that observed for other RGG motif bearing peptides. These data reveal that the hnRNP U RBD attenuates the RNA binding selectivity of its core RGG motifs to achieve an extensive RNA interactome. We propose that a critical role of RGG/RG motifs in RNA biology is to alter binding affinity or selectivity of adjacent RNA-binding domains.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141598061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural Basis for the Interaction Between Yeast Chromatin Assembly Factor 1 and Proliferating Cell Nuclear Antigen","authors":"","doi":"10.1016/j.jmb.2024.168695","DOIUrl":"10.1016/j.jmb.2024.168695","url":null,"abstract":"<div><p>Proliferating cell nuclear antigen (PCNA), the homotrimeric eukaryotic sliding clamp protein, recruits and coordinates the activities of a multitude of proteins that function on DNA at the replication fork. Chromatin assembly factor 1 (CAF-1), one such protein, is a histone chaperone that deposits histone proteins onto DNA immediately following replication. The interaction between CAF-1 and PCNA is essential for proper nucleosome assembly at silenced genomic regions. Most proteins that bind PCNA contain a PCNA-interacting peptide (PIP) motif, a conserved motif containing only eight amino acids. Precisely how PCNA is able to discriminate between binding partners at the replication fork using only these small motifs remains unclear. Yeast CAF-1 contains a PIP motif on its largest subunit, Cac1. We solved the crystal structure of the PIP motif of CAF-1 bound to PCNA using a new strategy to produce stoichiometric quantities of one PIP motif bound to each monomer of PCNA. The PIP motif of CAF-1 binds to the hydrophobic pocket on the front face of PCNA in a similar manner to most known PIP-PCNA interactions. However, several amino acids immediately flanking either side of the PIP motif bind the IDCL or C-terminus of PCNA, as observed for only a couple other known PIP-PCNA interactions. Furthermore, mutational analysis suggests positively charged amino acids in these flanking regions are responsible for the low micromolar affinity of CAF-1 for PCNA, whereas the presence of a negative charge upstream of the PIP prevents a more robust interaction with PCNA. These results provide additional evidence that positive charges within PIP-flanking regions of PCNA-interacting proteins are crucial for specificity and affinity of their recruitment to PCNA at the replication fork.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141537204","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structural Insights into Ciona intestinalis Septins: Complexes Suggest a Mechanism for Nucleotide-dependent Interfacial Cross-talk","authors":"Deborah C. Mendonça ,&nbsp;Sinara T.B. Morais ,&nbsp;Heloísa Ciol ,&nbsp;Andressa P.A. Pinto ,&nbsp;Diego A. Leonardo ,&nbsp;Humberto D’Muniz Pereira ,&nbsp;Napoleão F. Valadares ,&nbsp;Rodrigo V. Portugal ,&nbsp;Bruno P. Klaholz ,&nbsp;Richard C. Garratt ,&nbsp;Ana P.U. Araujo","doi":"10.1016/j.jmb.2024.168693","DOIUrl":"10.1016/j.jmb.2024.168693","url":null,"abstract":"<div><p>Septins are filamentous nucleotide-binding proteins which can associate with membranes in a curvature-dependent manner leading to structural remodelling and barrier formation. <em>Ciona intestinalis,</em> a model for exploring the development and evolution of the chordate lineage, has only four septin-coding genes within its genome. These represent orthologues of the four classical mammalian subgroups, making it a minimalist non-redundant model for studying the modular assembly of septins into linear oligomers and thereby filamentous polymers. Here, we show that <em>C. intestinalis</em> septins present a similar biochemistry to their human orthologues and also provide the cryo-EM structures of an octamer, a hexamer and a tetrameric sub-complex. The octamer, which has the canonical arrangement (2-6-7-9-9-7-6-2) clearly shows an exposed NC-interface at its termini enabling copolymerization with hexamers into mixed filaments. Indeed, only combinations of septins which had <em>Ci</em>SEPT2 occupying the terminal position were able to assemble into filaments via NC-interface association. The <em>Ci</em>SEPT7-<em>Ci</em>SEPT9 tetramer is the smallest septin particle to be solved by Cryo-EM to date and its good resolution (2.7 Å) provides a well-defined view of the central NC-interface. On the other hand, the <em>Ci</em>SEPT7-<em>Ci</em>SEPT9 G-interface shows signs of fragility permitting toggling between hexamers and octamers, similar to that seen in human septins but not in yeast. The new structures provide insights concerning the molecular mechanism for cross-talk between adjacent interfaces. This indicates that <em>C. intestinalis</em> may represent a valuable tool for future studies, fulfilling the requirements of a complete but simpler system to understand the mechanisms behind the assembly and dynamics of septin filaments.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141496656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phospholipid Supply for Autophagosome Biogenesis","authors":"","doi":"10.1016/j.jmb.2024.168691","DOIUrl":"10.1016/j.jmb.2024.168691","url":null,"abstract":"<div><p>Autophagy is a cellular degradation pathway where double-membrane autophagosomes form <em>de novo</em> to engulf cytoplasmic material destined for lysosomal degradation. This process requires regulated membrane remodeling, beginning with the initial autophagosomal precursor and progressing to its elongation and maturation into a fully enclosed, fusion-capable vesicle. While the core protein machinery involved in autophagosome formation has been extensively studied over the past two decades, the role of phospholipids in this process has only recently been studied. This review focuses on the phospholipid composition of the phagophore membrane and the mechanisms that supply lipids to expand this unique organelle.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022283624002936/pdfft?md5=c8aed4ab852cfdaf7d55affa3485bcb7&pid=1-s2.0-S0022283624002936-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141465121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Molecular Mechanisms and Physiological Functions of Autophagy","authors":"","doi":"10.1016/j.jmb.2024.168692","DOIUrl":"10.1016/j.jmb.2024.168692","url":null,"abstract":"","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022283624002948/pdfft?md5=230e48b863d43ca77a70195641ad71a8&pid=1-s2.0-S0022283624002948-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141465120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The HIV-1 Transcriptional Program: From Initiation to Elongation Control.","authors":"Iván D'Orso","doi":"10.1016/j.jmb.2024.168690","DOIUrl":"10.1016/j.jmb.2024.168690","url":null,"abstract":"<p><p>A large body of work in the last four decades has revealed the key pillars of HIV-1 transcription control at the initiation and elongation steps. Here, I provide a recount of this collective knowledge starting with the genomic elements (DNA and nascent TAR RNA stem-loop) and transcription factors (cellular and the viral transactivator Tat), and later transitioning to the assembly and regulation of transcription initiation and elongation complexes, and the role of chromatin structure. Compelling evidence support a core HIV-1 transcriptional program regulated by the sequential and concerted action of cellular transcription factors and Tat to promote initiation and sustain elongation, highlighting the efficiency of a small virus to take over its host to produce the high levels of transcription required for viral replication. I summarize new advances including the use of CRISPR-Cas9, genetic tools for acute factor depletion, and imaging to study transcriptional dynamics, bursting and the progression through the multiple phases of the transcriptional cycle. Finally, I describe current challenges to future major advances and discuss areas that deserve more attention to both bolster our basic knowledge of the core HIV-1 transcriptional program and open up new therapeutic opportunities.</p>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141465123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Elucidating the Activation Mechanism of the Proton-sensing GPR68 Receptor","authors":"Christos Matsingos ,&nbsp;Lesley A. Howell ,&nbsp;Peter J. McCormick ,&nbsp;Arianna Fornili","doi":"10.1016/j.jmb.2024.168688","DOIUrl":"10.1016/j.jmb.2024.168688","url":null,"abstract":"<div><p>GPR68 is a proton-sensing G-protein Coupled Receptor (GPCR) involved in a variety of physiological processes and disorders including neoplastic pathologies. While GPR68 and few other GPCRs have been shown to be activated by a decrease in the extracellular pH, the molecular mechanism of their activation remains largely unknown. In this work, we used a combined computational and <em>in vitro</em> approach to provide new insight into the activation mechanism of the receptor. Molecular Dynamics simulations of GPR68 were used to model the changes in residue interactions and motions triggered by pH. Global and local rearrangements consistent with partial activation were observed upon protonation of the inactive state. Selected extracellular histidine and transmembrane acidic residues were found to have significantly upshifted p<em>K</em>_a values during the simulations, consistently with their previously hypothesised role in activation through changes in protonation state. Moreover, a novel pairing between histidine and acidic residues in the extracellular region was highlighted by both sequence analyses and simulation data and tested through site-directed mutagenesis. At last, we identified a previously unknown hydrophobic lock in the extracellular region that might stabilise the inactive conformation and regulate the transition to the active state.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0022283624002900/pdfft?md5=11f80a2c5a4b5bdba6ea197f0b7a9396&pid=1-s2.0-S0022283624002900-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141465119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Structural Stability of Membrane Proteins Revisited: Combined Thermodynamic and Spectral Phasor Analysis of SDS-induced Denaturation of a Thermophilic Cu(I)-transport ATPase","authors":"Alvaro A. Recoulat Angelini,&nbsp;Ernesto A. Roman,&nbsp;F. Luis González Flecha","doi":"10.1016/j.jmb.2024.168689","DOIUrl":"10.1016/j.jmb.2024.168689","url":null,"abstract":"<div><p>Assessing membrane protein stability is among the major challenges in protein science due to their inherent complexity, which complicates the application of conventional biophysical tools. In this work, sodium dodecyl sulfate-induced denaturation of <em>Af</em>CopA, a Cu(I)-transport ATPase from <em>Archaeoglobus fulgidus</em>, was explored using a combined model-free spectral phasor analysis and a model-dependent thermodynamic analysis. Decrease in tryptophan and 1-anilino-naphthalene-8-sulfonate fluorescence intensity, displacements in the spectral phasor space, and the loss of ATPase activity were reversibly induced by this detergent. Refolding from the SDS-induced denatured state yields an active enzyme that is functionally and spectroscopically indistinguishable from the native state of the protein. Phasor analysis of Trp spectra allowed us to identify two intermediate states in the SDS-induced denaturation of <em>Af</em>CopA, a result further supported by principal component analysis. In contrast, traditional thermodynamic analysis detected only one intermediate state, and including the second one led to overparameterization. Additionally, ANS fluorescence spectral analysis detected one more intermediate and a gradual change at the level of the hydrophobic transmembrane surface of the protein. Based on this evidence, a model for acquiring the native structure of <em>Af</em>CopA in a membrane-like environment is proposed.</p></div>","PeriodicalId":369,"journal":{"name":"Journal of Molecular Biology","volume":null,"pages":null},"PeriodicalIF":4.7,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141465124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}