Structural characterization of HIV gp41 with the membrane-proximal external region.
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.
Center for Synchrotron Biosciences, Case Western Reserve University, Cleveland, OH 44106, USA. wushi@bnl.gov
Wuxian
W
Shi
Jen
J
Bohon
Dong P
DP
Han
Habtom
H
Habte
Yali
Y
Qin
Michael W
MW
Cho
Mark R
MR
Chance
D016915:AIDS Vaccines / Q000737:chemistry; D000595:Amino Acid Sequence; D000941:Antigens / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism*; D018360:Crystallography, X-Ray / Q000379:methods; D015195:Drug Design; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D000939:Epitopes / Q000737:chemistry; D015700:HIV Envelope Protein gp41 / Q000737:chemistry*; D015497:HIV-1 / Q000378:metabolism*; D017665:Hydroxyl Radical; D013058:Mass Spectrometry / Q000379:methods; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation
D016915:AIDS Vaccines; D000941:Antigens; D000939:Epitopes; D015700:HIV Envelope Protein gp41; D017665:Hydroxyl Radical