Structural and Functional Studies on the Extracellular Domain of Bst2/Tetherin in Reduced and Oxidized Conformations.Schubert, H.L., Zhai, Q., Sandrin, V., Eckert, D.M., Garcia-Maya, M., Saul, L., Sundquist, W.I., Steiner, R.A., Hill, C.P.
(2010) Proc.Natl.Acad.Sci.USA 107: 17951
- PubMed: 20880831
- DOI: 10.1073/pnas.1008206107
- Primary Citation of Related Structures:
- PubMed 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 ...
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.
Department of Biochemistry, University of Utah School of Medicine, Salt Lake City, UT 84112-5650, USA.