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Title: Structure and Glycan Binding of a New Cyanovirin-N Homolog

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
National Institutes of Health (NIH)
OSTI Identifier:
1330888
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Biological Chemistry; Journal Volume: 291; Journal Issue: 36
Country of Publication:
United States
Language:
ENGLISH

Citation Formats

Matei, Elena, Basu, Rohan, Furey, William, Shi, Jiong, Calnan, Conor, Aiken, Christopher, and Gronenborn, Angela M. Structure and Glycan Binding of a New Cyanovirin-N Homolog. United States: N. p., 2016. Web. doi:10.1074/jbc.M116.740415.
Matei, Elena, Basu, Rohan, Furey, William, Shi, Jiong, Calnan, Conor, Aiken, Christopher, & Gronenborn, Angela M. Structure and Glycan Binding of a New Cyanovirin-N Homolog. United States. doi:10.1074/jbc.M116.740415.
Matei, Elena, Basu, Rohan, Furey, William, Shi, Jiong, Calnan, Conor, Aiken, Christopher, and Gronenborn, Angela M. 2016. "Structure and Glycan Binding of a New Cyanovirin-N Homolog". United States. doi:10.1074/jbc.M116.740415.
@article{osti_1330888,
title = {Structure and Glycan Binding of a New Cyanovirin-N Homolog},
author = {Matei, Elena and Basu, Rohan and Furey, William and Shi, Jiong and Calnan, Conor and Aiken, Christopher and Gronenborn, Angela M.},
abstractNote = {},
doi = {10.1074/jbc.M116.740415},
journal = {Journal of Biological Chemistry},
number = 36,
volume = 291,
place = {United States},
year = 2016,
month = 7
}
  • The host factor Hfq, as the bacterial branch of the Sm family, is an RNA-binding protein involved in the post-transcriptional regulation of mRNA expression and turnover. Hfq facilitates pairing between small regulatory RNAs (sRNAs) and their corresponding mRNA targets by binding both RNAs and bringing them into close proximity. Hfq homologs self-assemble into homo-hexameric rings with at least two distinct surfaces that bind RNA. Recently, another binding site, dubbed the `lateral rim', has been implicated in sRNA·mRNA annealing; the RNA-binding properties of this site appear to be rather subtle, and its degree of evolutionary conservation is unknown. An Hfq homologmore » has been identified in the phylogenetically deep-branching thermophileAquifex aeolicus(Aae), but little is known about the structure and function of Hfq from basal bacterial lineages such as the Aquificae. Therefore,AaeHfq was cloned, overexpressed, purified, crystallized and biochemically characterized. Structures ofAaeHfq were determined in space groupsP1 andP6, both to 1.5 Å resolution, and nanomolar-scale binding affinities for uridine- and adenosine-rich RNAs were discovered. Co-crystallization with U 6RNA reveals that the outer rim of theAaeHfq hexamer features a well defined binding pocket that is selective for uracil. ThisAaeHfq structure, combined with biochemical and biophysical characterization of the homolog, reveals deep evolutionary conservation of the lateral RNA-binding mode, and lays a foundation for further studies of Hfq-associated RNA biology in ancient bacterial phyla.« less
  • ABSTRACT All HIV-1-infected individuals develop strain-specific neutralizing antibodies to their infecting virus, which in some cases mature into broadly neutralizing antibodies. Defining the epitopes of strain-specific antibodies that overlap conserved sites of vulnerability might provide mechanistic insights into how broadly neutralizing antibodies arise. We previously described an HIV-1 clade C-infected donor, CAP257, who developed broadly neutralizing plasma antibodies targeting an N276 glycan-dependent epitope in the CD4 binding site. The initial CD4 binding site response potently neutralized the heterologous tier 2 clade B viral strain RHPA, which was used to design resurfaced gp120 antigens for single-B-cell sorting. Here we report themore » isolation and structural characterization of CAP257-RH1, an N276 glycan-dependent CD4 binding site antibody representative of the early CD4 binding site plasma response in donor CAP257. The cocrystal structure of CAP257-RH1 bound to RHPA gp120 revealed critical interactions with the N276 glycan, loop D, and V5, but not with aspartic acid 368, similarly to HJ16 and 179NC75. The CAP257-RH1 monoclonal antibody was derived from the immunoglobulin-variable IGHV3-33 and IGLV3-10 genes and neutralized RHPA but not the transmitted/founder virus from donor CAP257. Its narrow neutralization breadth was attributed to a binding angle that was incompatible with glycosylated V5 loops present in almost all HIV-1 strains, including the CAP257 transmitted/founder virus. Deep sequencing of autologous CAP257 viruses, however, revealed minority variants early in infection that lacked V5 glycans. These glycan-free V5 loops are unusual holes in the glycan shield that may have been necessary for initiating this N276 glycan-dependent CD4 binding site B-cell lineage. IMPORTANCEThe conserved CD4 binding site on gp120 is a major target for HIV-1 vaccine design, but key events in the elicitation and maturation of different antibody lineages to this site remain elusive. Studies have shown that strain-specific antibodies can evolve into broadly neutralizing antibodies or in some cases act as helper lineages. Therefore, characterizing the epitopes of strain-specific antibodies may help to inform the design of HIV-1 immunogens to elicit broadly neutralizing antibodies. In this study, we isolate a narrowly neutralizing N276 glycan-dependent antibody and use X-ray crystallography and viral deep sequencing to describe how gp120 lacking glycans in V5 might have elicited these early glycan-dependent CD4 binding site antibodies. These data highlight how glycan holes can play a role in the elicitation of B-cell lineages targeting the CD4 binding site.« less
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  • No abstract prepared.