25-30 August 2019
Henry Ford Building
Europe/Berlin timezone

The NMR structure of a gp41 cytoplasmic tail fragment reveals the structural basis of the transmembrane coupling of the HIV-1 envelope glycoprotein

26 Aug 2019, 12:30
30m
Lecture Hall A (Henry Ford Building)

Lecture Hall A

Henry Ford Building

Talk Biological applications Biomolecules

Speaker

Dr Alessandro Piai (Harvard Medical School)

Description

The antigenic structure of the HIV-1 envelope spike (Env) is a major consideration for vaccine design to induce effective immune responses. Recent studies suggest that the cytoplasmic tail (CT) of Env influences the antigenic properties of its ectodomain on the opposite side of membrane, but the structural basis of this conformational coupling is still unknown. Using nuclear magnetic resonance (NMR) spectroscopy, we determined the structure in near-lipid bilayer environment of an Env fragment encompassing the transmembrane domain (TMD) and a large portion of the CT, containing the Kennedy sequence (KS) and the lentivirus lytic peptide 2 (LLP2). Structure calculation faced the challenge of constraining the amphipathic CT at the water-lipid interface, which was overcome by implementing plane restraints obtained from NMR-based membrane partition analysis of the protein in bicelles. The structure revealed a molecular architecture never observed before, in which the CT folds into amphipathic helices attaching to the membrane and wraps around the C-terminal end of the TMD, thereby forming a support baseplate for the rest of Env. Biochemical data indicated that the CT-TMD interaction is important for the CT folding and trimerization, which help stabilizing the native conformation of the Env. Functional data from pseudovirus-based neutralization assays confirmed that loosening or disruption of the CT-TMD interaction can indeed affect the antibody binding to the Env ectodomain at the other side of the membrane, as weakening of the CT baseplate can destabilize the conformation of the TMD, which in turn affects that of the membrane-proximal external region (MPER) and the rest of the Env ectodomain, shifting it toward an open conformation. These results contribute to explaining why the CT has a profound effect on the antigenic structure of the ectodomain and can guide HIV-1 immunogen design.

Primary authors

Dr Alessandro Piai (Harvard Medical School) Dr Qingshan Fu (Harvard Medical School) Dr Wen Chen (Harvard Medical School) Prof. James J. Chou (Harvard Medical School)

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