Fig. 2

Location of Ser143 and Val255 in the prefusogenic structure of a Clade B HIV-1 Env trimer (PDB: 5FUU) [9]. A Env subunits gp120 (gray) and gp41 (pale yellow) are shown in cartoon representation with surface rendering of one gp120 subunit. Ser143 is located in the flexible V1 loop (orange) on the apical surface while Val255 (red) is located in a cavity that forms part of the putative PT binding pocket. B Enlargement of the PT binding cavity showing the positions of Trp 112 and Ser375 (green) [15, 19] that define the two subcavities of the PT binding site and the β20-21 loop (blue) that plays a critical role in Env activation