Figure 1. Structure of the HIV-1 Env TMD trimer in bicelles.
The protein construct used for structure determination is a fragment of gp41 (residues 677-716), derived from a clade D HIV-1 isolate 92UG024.2. The bicelles are formed with 1,2-Dimyristoyl-sn-Glycero-3-Phosphocholine (DMPC) and 1,2-Dihexanoyl-sn-Glycero-3-Phosphocholine (DHPC) at a molar ratio of 0.5. The approximate placement of the trimer structure in the presumed DMPC bilayer, which is slightly thinner than the characterized thickness of DOPC bilayer (35), was based on the solvent paramagnetic relaxation enhancement of the four arginines (R683, R696, R707, and R709) [21].