Structural Characterization of HIV gp41 with the Membrane-proximal External Region |
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Authors: | Wuxian Shi Jen Bohon Dong P. Han Habtom Habte Yali Qin Michael W. Cho Mark R. Chance |
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Affiliation: | From the ‡Center for Synchrotron Biosciences.;§Center for Proteomics and Bioinformatics, and ;‖Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106 and ;the ¶Department of Biomedical Sciences, College of Veterinary Medicine, Iowa State University, Ames, Iowa 50011-1250 |
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Abstract: | Human immunodeficiency virus, type 1 (HIV-1) envelope glycoprotein (gp120/gp41) plays a critical role in virus infection and pathogenesis. Three of the six monoclonal antibodies considered to have broadly neutralizing activities (2F5, 4E10, and Z13e1) bind to the membrane-proximal external region (MPER) of gp41. This makes the MPER a desirable template for developing immunogens that can elicit antibodies with properties similar to these monoclonal antibodies, with a long term goal of developing antigens that could serve as novel HIV vaccines. In order to provide a structural basis for rational antigen design, an MPER construct, HR1-54Q, was generated for x-ray crystallographic and x-ray footprinting studies to provide both high resolution atomic coordinates and verification of the solution state of the antigen, respectively. The crystal structure of HR1-54Q reveals a trimeric, coiled-coil six-helical bundle, which probably represents a postfusion form of gp41. The MPER portion extends from HR2 in continuation of a slightly bent long helix and is relatively flexible. The structures observed for the 2F5 and 4E10 epitopes agree well with existing structural data, and enzyme-linked immunosorbent assays indicate that the antigen binds well to antibodies that recognize the above epitopes. Hydroxyl radical-mediated protein footprinting of the antigen in solution reveals specifically protected and accessible regions consistent with the predictions based on the trimeric structure from the crystallographic data. Overall, the HR1-54Q antigen, as characterized by crystallography and footprinting, represents a postfusion, trimeric form of HIV gp41, and its structure provides a rational basis for gp41 antigen design suitable for HIV vaccine development. |
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Keywords: | Antigen Glycoprotein HIV Protein Structure X-ray Crystallography X-ray Footprinting Vaccine Design |
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