Structural insight into the mechanisms of enveloped virus tethering by tetherin

Abstract

Tetherin/BST2 is a type-II membrane protein that inhibits the release of a range of enveloped viruses, including HIV-1. Here we report three crystal structures of human tetherin, including the fulllength ectodomain, a triple cysteine mutant and an ectodomain truncation. These structures show that tetherin forms a continuous alpha helix encompassing almost the entire ectodomain. Tetherin helices dimerize into parallel coiled coils via interactions throughout the C-terminal portion of the ectodomain. A comparison of the multiple structures of the tetherin dimer reveals inherent constrained flexibility at two hinges positioned at residues A88 and G109. In the crystals, two tetherin ectodomain dimers associate into a tetramer by forming an antiparallel four-helix bundle at their N termini. However, mutagenesis studies suggest that the tetrametric form of tetherin, although potentially contributing to, is not essential for its antiviral activity. Nonetheless, the structural and chemical properties of the N terminus of the ectodomain are important for optimal tethering function. This study provides detailed insight into the mechanisms by which this broad-spectrum antiviral restriction factor can function.transmembrane | disulfide bonds | stability | budding

Structural insight into HIV-1 capsid recognition by rhesus TRIM5α

“…We investigated the oligomerization state of PRY/SPRY rh and PRY/SPRY hu . To overcome the poor yield and solubility problem of TRIM5α PRY/SPRY, either PRY/SPRY rh or PRY/SPRY hu was fused to the end of the Cterminal helix of the maltose binding protein (MBP) (25), resulting in MBP-PRY/SPRY rh275 (residues 275-493) and MBP-PRY/SPRY hu273 (residues 273-489). Typical yields for these fusion proteins were over 10 mg/L of Escherichia coli cells.…”

The Size and Conservation of a Coiled-coil Structure in the Ectodomain of Human BST-2/Tetherin Is Dispensable for Inhibition of HIV-1 Virion Release

“…1A). Structural analyses of BST-2 indicate that the BST-2 ectodomain forms a continuous ␣-helix that forms a parallel dimeric coiled-coil in its C-terminal region (25)(26)(27)(28). However, the precise role of the coiled-coil and, in particular, possible constraints regarding the size of the coiled-coil remain unclear.…”

“…Images were generated using the POV-Ray function within YASARA. For comparison of all the structures of BST-2, 3MQ7 (27), 3MQC (27), 3MQB (27), 3NWH (26), and 2XG7 (26) were aligned using the superpose function within YASARA 12.4.1.…”

“…The Structure of the Ectodomain of BST-2 at Its N Terminus Is Flexible-Recent studies revealed the crystallographic structure of the human and mouse BST-2 ectodomain (25)(26)(27)(28). We compiled the full-length structures of human BST-2 deposited into the RCSB PDB protein database using YASARA (Fig.…”

“…However, we recently found evidence to suggest that the C-terminal membrane anchor could be a second transmembrane domain rather than a glycosylphosphatidylinositol anchor (24). The two TM domains are separated by ϳ120 residues that constitute the ectodomain of the protein, which is predicted to form a coiled-coil structure (25)(26)(27)(28). The N-terminal half of the BST-2 ectodomain contains three cysteine residues, which are involved in the formation of covalent cysteinelinked dimers (20,21,29,30).…”