FIG 2.

PERV TM displays a 6HB stabilized by electrostatic interactions. (A) Annotated ribbon representation of the PERV TM_493–587 structure. The frontmost protomer is color-coded according to the schematic presented in Fig. 1A. Key functional and structural regions of the PERV TM are annotated. (B) Representative 2|F_o| − |F_c| electron density map contoured at 1σ and superimposed on the final refined PERV TM structure. Strong, well-defined electron density is observed throughout the HR1, CR, tether, and HR2 regions. (C) Helical wheel analysis of the central PERV HR1 trimer coiled-coil from residues 499 to 520 (helix turns 2 to 6) with the heptad repeat labeled a to g. Hydrophobic, polar, negatively charged and positively charged residues are colored yellow, green, red, and blue, respectively. Residue numbering is presented in one of the helical protomers. The presence of ⁵⁰⁶VTED⁵⁰⁹ in the PERV TM (highlighted with asterisks) results in a stutter of the heptad repeat, where it disrupts the periodicity of hydrophobic residues at the a and d positions of the heptad repeat.