Structural characterization of HIV-1 Env heterotrimers bound to one or two CD4 receptors reveals intermediate Env conformations
Abstract
HIV-1 envelope (Env) exhibits distinct conformational changes in response to host receptor (CD4) engagement. Env, a trimer of gp120/gp41 heterodimers, has been structurally characterized in a closed, prefusion conformation with closely associated gp120s and coreceptor binding sites on gp120 V3 hidden by V1V2 loops, and in fully-saturated CD4-bound open Env conformations with changes including outwardly rotated gp120s and displaced V1V2 loops. To investigate changes resulting from sub-stoichiometric CD4 binding, we solved 3.4Å and 3.9Å single-particle cryo-EM structures of soluble, native-like Envs bound to one or two CD4 molecules. Env trimer bound to one CD4 adopted the closed, prefusion Env state. When bound to two CD4s, the CD4-bound gp120s exhibited an open Env conformation including a four-stranded gp120 bridging sheet and displaced gp120 V1V2 loops that expose the coreceptor sites on V3. The third gp120 adopted an intermediate, occluded-open state that included gp120 outward rotation but maintained the prefusion, three-stranded gp120 bridging sheet and showed only partial V1V2 displacement and V3 exposure. We conclude that engagement of one CD4 molecule was insufficient to stimulate CD4-induced conformational changes, while binding two CD4 molecules led to Env opening in CD4-bound protomers only. Together, these results illuminate HIV-1 Env intermediate conformations and illustrate the structural plasticity of HIV-1 Env.
Additional Information
The copyright holder for this preprint is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under a CC-BY-NC-ND 4.0 International license. We thank W. Mothes and W. Li, and Z. Qin (Yale University) for sharing cryo-ET data, J. Vielmetter, A. Rorick, K. Storm, and the Protein Expression Center in the Beckman Institute at Caltech for expression assistance, J.E. Robinson (Tulane University) for the JR-52 antibody. Electron microscopy was performed in the Caltech Cryo-EM Center with assistance from S. Chen, and A. DeLaitsch for comments on the manuscript. This work was supported by the NIH P50 AI150464 (P.J.B.), National Institute of Allergy and Infectious Diseases (NIAID) Grant HIVRAD P01 AI100148 (to P.J.B.), and the Bill and Melinda Gates Foundation Collaboration for AIDS Vaccine Discovery (CAVD) grant INV-002143 (P.J.B.). The contents of this publication are solely the responsibility of the authors and do not necessarily represent the official views of NIAID or NIH. Author contributions. K.A.D., C.F., and P.J.B. designed the research. K.A.D. designed Env constructs, performed protein purification, and conducted ELISAs. C.F. collected structural data. Z.Y. created Supplementary Movie 1. K.A.D., C.F., Z.Y., and P.J.B. analyzed results. K.A.D. and P.J.B. wrote the manuscript with input from co-authors. The authors have declared no competing interest.Attached Files
Submitted - 2023.01.27.525985v1.full.pdf
Supplemental Material - media-1.pdf
Supplemental Material - media-2.mp4
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Additional details
- Eprint ID
- 120145
- Resolver ID
- CaltechAUTHORS:20230316-182374000.28
- P50 AI150464
- NIH
- HIVRAD P01 AI100148
- NIH
- INV-002143
- Bill and Melinda Gates Foundation
- Created
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2023-03-20Created from EPrint's datestamp field
- Updated
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2023-03-20Created from EPrint's last_modified field
- Caltech groups
- Division of Biology and Biological Engineering