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. 2021 Oct 27;95(22):e01050-21. doi: 10.1128/JVI.01050-21

FIG 1.

FIG 1

gB structures. (A) Postfusion HSV-1 gB trimer (PDB accession number 2GUM) (5). Domain I (DI) (blue), including the fusion loops (magenta), sits closest to the membrane. Domain III (DIII) (yellow) includes a large central trimer of helices, with the N termini down (yellow N) and the C termini up (yellow C). Domain V (DV) (red) packs against the domain III helices in an antiparallel orientation down the length of the structure, with domain V from one protomer contacting domain III from the other two protomers. The residues mutated in gB3A (red space-filled residues I671, H681, and F683) form extensive contacts with domain III. Domain II (DII) (green) and domain IV (DIV) (orange) are also shown. (B) Prefusion model of HSV-1 gB (PDB accession number 6Z9M) (15). Domains I to V and the fusion loops are colored as described above for panel A. A transparent surface rendering of the gB trimer is shown, with a single protomer shown in ribbon format. Domain I comprises the legs of the trimer with fusion loops facing the membrane. Domain III includes a long helix at the center of the trimer with its N terminus up (yellow N label) and its C terminus down (yellow C label), the opposite orientation compared to the postfusion structure. Domain V includes an extended strand at its N terminus (red N label) and a central helix at its C terminus (red C label) that descends toward the membrane. The domain V extended strand is packed between the domains of a neighboring protomer. I671, H681, and F683 (red space-filled residues) are positioned near the top and bottom of this strand. (C) Ribbon model of prefusion HSV-1 gB with an inset. The prefusion trimer from panel B is shown in ribbon format with the same coloring. The extended strand of domain V packs between domains I (blue), II (green), and III (yellow) of a neighboring protomer. The inset shows I671, H681, and F683 in one protomer (red sticks) and their contacts in the neighboring protomer (space-filled residues). I671 contacts domain II residue K151 (green) and domain III residue R557 (yellow). H681 contacts domain III at residue T120 (yellow) and domain I at two sites, Y165 (blue) and T291 (blue). F683 contacts domain I at R189 (blue) as well as at G292 and D293 (blue). A contact is defined as a location within a 4-Å proximity.