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Structural and functional studies on the extracellular domain of BST2/tetherin in reduced and oxidized conformations

DOI: 10.1073/pnas.1008206107 DOI Help
PMID: 20880831 PMID Help

Authors: Heidi L. Schubert (University of Utah) , Qianting Zhai (University of Utah) , Virginie Sandrin (University of Utah) , Debra M. Eckert (University of Utah) , Mitla Garcia-maya (King's College London) , Louise Saul (King's College London) , Wesley I. Sundquist (University of Utah) , Roberto A. Steiner (King's College London) , Christopher P. Hill (University of Utah)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 107 (42) , PAGES 17951 - 17956

State: Published (Approved)
Published: October 2010
Diamond Proposal Number(s): 1220

Abstract: HIV-1 and other enveloped viruses can be restricted by a host cellular protein called BST2/tetherin that prevents release of budded viruses from the cell surface. Mature BST2 contains a small cytosolic region, a predicted transmembrane helix, and an extracellular domain with a C-terminal GPI anchor. To advance understanding of BST2 function, we have determined a 2.6 Å crystal structure of the extracellular domain of the bacterially expressed recombinant human protein, residues 47–152, under reducing conditions. The structure forms a single long helix that associates as a parallel dimeric coiled coil over its C-terminal two-thirds, while the N-terminal third forms an antiparallel four-helix bundle with another dimer, creating a global tetramer. We also report the 3.45 Å resolution structure of BST2(51-151) prepared by expression as a secreted protein in HEK293T cells. This oxidized construct forms a dimer in the crystal that is superimposable with the reduced protein over the C-terminal two-thirds of the molecule, and its N terminus suggests pronounced flexibility. Hydrodynamic data demonstrated that BST2 formed a stable tetramer under reducing conditions and a dimer when oxidized to form disulfide bonds. A mutation that selectively disrupted the tetramer (L70D) increased protein expression modestly but only reduced antiviral activity by approximately threefold. Our data raise the possibility that BST2 may function as a tetramer at some stage, such as during trafficking, and strongly support a model in which the primary functional state of BST2 is a parallel disulfide-bound coiled coil that displays flexibility toward its N terminus.

Journal Keywords: CD; Biopolymers; Crystallography; X-Ray; GPI-Linked; Humans; Oxidation-Reduction; Protein; Structure-Activity Relationship

Subject Areas: Biology and Bio-materials, Medicine, Chemistry

Instruments: I02-Macromolecular Crystallography , I03-Macromolecular Crystallography , I04-Macromolecular Crystallography

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