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Crystal structure of HIV-1 capsid protein (p24) in complex with Fab13B5Crystal structure of HIV-1 capsid protein (p24) in complex with Fab13B5
Structural highlights
Function[GAG_HV1H2] Matrix protein p17 targets Gag and Gag-Pol polyproteins to the plasma membrane via a multipartite membrane binding signal, that includes its myristoylated N-terminus. Also mediates nuclear localization of the preintegration complex. Implicated in the release from host cell mediated by Vpu. Capsid protein p24 forms the conical core of the virus that encapsulates the genomic RNA-nucleocapsid complex. Nucleocapsid protein p7 encapsulates and protects viral dimeric unspliced (genomic) RNA. Binds these RNAs through its zinc fingers. p6-gag plays a role in budding of the assembled particle by interacting with the host class E VPS proteins TSG101 and PDCD6IP/AIP1 (By similarity). Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBACKGROUND: Elucidating the structural basis of antigen-antibody recognition ideally requires a structural comparison of free and complexed components. To this end we have studied a mouse monoclonal antibody, denoted 13B5, raised against p24, the capsid protein of HIV-1. We have previously described the first crystal structure of intact p24 as visualized in the Fab13B5-p24 complex. Here we report the structure of the uncomplexed Fab13B5 at 1.8 A resolution and analyze the Fab-p24 interface and the conformational changes occurring upon complex formation. RESULTS: Fab13B5 recognizes a nearly continuous epitope comprising a helix-turn-helix motif in the C-terminal domain of p24. Only 4 complementarity-determining regions (CDRs) are in contact with p24 with most interactions being by the heavy chain. Comparison of the free and complexed Fab reveals that structural changes upon binding are localized to a few side chains of CDR-H1 and -H2 but involve a larger, concerted displacement of CDR-H3. Antigen binding is also associated with an 8 degrees relative rotation of the heavy and light chain variable regions. In p24, small conformational changes localized to the turn between the two helices comprising the epitope result from Fab binding. CONCLUSIONS: The relatively small area of contact between Fab13B5 and p24 may be related to the fact that the epitope is a continuous peptide rather than a more complex protein surface and correlates with a relatively low affinity of antigen and antibody. Despite this, a significant quaternary structural change occurs in the Fab upon complex formation, with additional smaller adaptations of both antigen and antibody. Mutual conformational adaptations in antigen and antibody upon complex formation between an Fab and HIV-1 capsid protein p24.,Monaco-Malbet S, Berthet-Colominas C, Novelli A, Battai N, Piga N, Cheynet V, Mallet F, Cusack S Structure. 2000 Oct 15;8(10):1069-77. PMID:11080628[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences |
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