11 research outputs found

    Crystal Structure of HIV-1 gp41 Including Both Fusion Peptide and Membrane Proximal External Regions

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    The HIV-1 envelope glycoprotein (Env) composed of the receptor binding domain gp120 and the fusion protein subunit gp41 catalyzes virus entry and is a major target for therapeutic intervention and for neutralizing antibodies. Env interactions with cellular receptors trigger refolding of gp41, which induces close apposition of viral and cellular membranes leading to membrane fusion. The energy released during refolding is used to overcome the kinetic barrier and drives the fusion reaction. Here, we report the crystal structure at 2 Å resolution of the complete extracellular domain of gp41 lacking the fusion peptide and the cystein-linked loop. Both the fusion peptide proximal region (FPPR) and the membrane proximal external region (MPER) form helical extensions from the gp41 six-helical bundle core structure. The lack of regular coiled-coil interactions within FPPR and MPER splay this end of the structure apart while positioning the fusion peptide towards the outside of the six-helical bundle and exposing conserved hydrophobic MPER residues. Unexpectedly, the section of the MPER, which is juxtaposed to the transmembrane region (TMR), bends in a 90°-angle sideward positioning three aromatic side chains per monomer for membrane insertion. We calculate that this structural motif might facilitate the generation of membrane curvature on the viral membrane. The presence of FPPR and MPER increases the melting temperature of gp41 significantly in comparison to the core structure of gp41. Thus, our data indicate that the ordered assembly of FPPR and MPER beyond the core contributes energy to the membrane fusion reaction. Furthermore, we provide the first structural evidence that part of MPER will be membrane inserted within trimeric gp41. We propose that this framework has important implications for membrane bending on the viral membrane, which is required for fusion and could provide a platform for epitope and lipid bilayer recognition for broadly neutralizing gp41 antibodies

    Crystal Structure and Size-Dependent Neutralization Properties of HK20, a Human Monoclonal Antibody Binding to the Highly Conserved Heptad Repeat 1 of gp41

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    The human monoclonal antibody (mAb) HK20 neutralizes a broad spectrum of primary HIV-1 isolates by targeting the highly conserved heptad repeat 1 (HR1) of gp41, which is transiently exposed during HIV-1 entry. Here we present the crystal structure of the HK20 Fab in complex with a gp41 mimetic 5-Helix at 2.3 Ã… resolution. HK20 employs its heavy chain CDR H2 and H3 loops to bind into a conserved hydrophobic HR1 pocket that is occupied by HR2 residues in the gp41 post fusion conformation. Compared to the previously described HR1-specific mAb D5, HK20 approaches its epitope with a different angle which might favor epitope access and thus contribute to its higher neutralization breadth and potency. Comparison of the neutralization activities of HK20 IgG, Fab and scFv employing both single cycle and multiple cycle neutralization assays revealed much higher potencies for the smaller Fab and scFv over IgG, implying that the target site is difficult to access for complete antibodies. Nevertheless, two thirds of sera from HIV-1 infected individuals contain significant titers of HK20-inhibiting antibodies. The breadth of neutralization of primary isolates across all clades, the higher potencies for C-clade viruses and the targeting of a distinct site as compared to the fusion inhibitor T-20 demonstrate the potential of HK20 scFv as a therapeutic tool

    Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

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    Joyce and the Subject of History

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    What did James Joyce think about history? He boasted that Dublin could be rebuilt from the pages of his novels, yet Joyce stopped writing essays and reviews at an age when many authors are just beginning to express themselves on important extra-literary topics--and the Joyce that emerges in biographies and memoirs is notoriously unreliable about history and politics. In Joyce and the Subject of History, some of the brightest stars in Joyce criticism tease out the historical implications embedded in Joyce\u27s oeuvre without conceding too much to the comprehensive historical claims of the fictions themselves. At a time when much historical work remains surprisingly under-theorized and much theoretical work excludes the detail and rigor of serious historical research, this collection attempts to bridge the gap between history and theory, to reconceive the field of literary historical scholarship as a whole. As an added resource, the book concludes with Robert Spoo\u27s extensive Annotated Bibliography of historical work on Joyce.https://digitalcommons.law.utulsa.edu/books/1021/thumbnail.jp

    Joyce and the Subject of History

    No full text
    What did James Joyce think about history? He boasted that Dublin could be rebuilt from the pages of his novels, yet Joyce stopped writing essays and reviews at an age when many authors are just beginning to express themselves on important extra-literary topics--and the Joyce that emerges in biographies and memoirs is notoriously unreliable about history and politics. In Joyce and the Subject of History, some of the brightest stars in Joyce criticism tease out the historical implications embedded in Joyce\u27s oeuvre without conceding too much to the comprehensive historical claims of the fictions themselves. At a time when much historical work remains surprisingly under-theorized and much theoretical work excludes the detail and rigor of serious historical research, this collection attempts to bridge the gap between history and theory, to reconceive the field of literary historical scholarship as a whole. As an added resource, the book concludes with Robert Spoo\u27s extensive Annotated Bibliography of historical work on Joyce.https://digitalcommons.law.utulsa.edu/books/1021/thumbnail.jp

    Tuftsin: Its Chemistry, Biology, and Clinical Potentia

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    Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

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    In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field
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