FIG. 6.

Residues of the BST-2 TMD potentially involved in an interaction with Vpu. Both genetic studies mapping residues under positive selection and functional studies have indicated that residues in the transmembrane domain (TMD) of human BST-2 are required for responsiveness to Vpu. Changes in these residues found in the BST-2 orthologs of nonhuman primates relative to the human protein account for the inactivity of HIV-1 Vpu against these proteins (see text for details). Remarkably, these residues are predominantly on one face of the TMD α-helix (highlighted in yellow), suggesting an interaction along that face with the TMD of Vpu. Image drawn using PyMOL.