title: Discovery of critical residues for viral entry and inhibition through structural Insight of HIV-1 fusion inhibitor CP621-652.
abstract: The core structure of HIV-1 gp41 is a stable six-helix bundle (6-HB) folded by its trimeric N- and C-terminal heptad repeats (NHR and CHR). We previously identified that the (621)QIWNNMT(627) motif located at the upstream region of gp41 CHR plays critical roles for the stabilization of the 6-HB core and peptide CP621-652 containing this motif is a potent HIV-1 fusion inhibitor, however, the molecular determinants underlying the stability and anti-HIV activity remained elusive. In this study, we determined the high-resolution crystal structure of CP621-652 complexed by T21. We find that the (621)QIWNNMT(627) motif does not maintain the α-helical conformation. Instead, residues Met(626) and Thr(627) form a unique hook-like structure (denoted as M-T hook), in which Thr(627) redirects the peptide chain to position Met(626) above the left side of the hydrophobic pocket on the NHR trimer. The side chain of Met(626) caps the hydrophobic pocket, stabilizing the interaction between the pocket and the pocket-binding domain. Our mutagenesis studies demonstrate that mutations of the M-T hook residues could completely abolish HIV-1 Env-mediated cell fusion and virus entry, and significantly destabilize the interaction of NHR and CHR peptides and reduce the anti-HIV activity of CP621-652. Our results identify an unusual structural feature that stabilizes the six-helix bundle, providing novel insights into the mechanisms of HIV-1 fusion and inhibition.
authors.affiliation: MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, 9 Dong Dan San Tiao, Beijing 100730, China.
authors.forename: Huihui
authors.initials: H
authors.lastname: Chong
authors.forename: Xue
authors.initials: X
authors.lastname: Yao
authors.forename: Zonglin
authors.initials: Z
authors.lastname: Qiu
authors.forename: Bo
authors.initials: B
authors.lastname: Qin
authors.forename: Ruiyun
authors.initials: R
authors.lastname: Han
authors.forename: Sandro
authors.initials: S
authors.lastname: Waltersperger
authors.forename: Meitian
authors.initials: M
authors.lastname: Wang
authors.forename: Sheng
authors.initials: S
authors.lastname: Cui
authors.forename: Yuxian
authors.initials: Y
authors.lastname: He
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D002460:Cell Line; D018360:Crystallography, X-Ray; D015700:HIV Envelope Protein gp41 / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D023581:HIV Fusion Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D010455:Peptides / Q000737:chemistry* / Q000494:pharmacology; D053586:Virus Internalization / Q000187:drug effects
chemical_list: D015700:HIV Envelope Protein gp41; D023581:HIV Fusion Inhibitors; D010455:Peptides; C514787:gp41 protein, Human immunodeficiency virus 1