Fig. 3.

FP and HR1_N conformation of HIV-1 Env trimer structures. a–c FP and HR1_N conformation of a the closed trimer structure (PDB accession code 5I8H), b the T/F100 trimer structure and c the open trimer structure (PDB accession code 5VN3). Only gp41 of each trimer structure are shown for clarity. The FP, FPPR, HR1_N, and the C-terminal part of HR2 (residues 637–664) regions of the trimer structures are shown as ribbon diagrams and semitransparent surfaces. Other parts of gp41 are shown only as surface representations. The three-fold axis of each structure is identified by a solid black triangle