Fig 4.

Functional region 1 (FR1) with fusion loops. (A) Ribbon representation of a gB protomer. The amino acid sequences of fusion loop 1 (FL1) (blue) and FL2 (cyan) are shown. The color scheme for the gB protomer is as published previously (4). The fusion loops are enlarged (box) to highlight individual amino acids. The colors of these residues correspond to the colors of the curves in panels B to E. (B) The DSP plasmids were used to measure the rates of fusion for FL1 mutants over 8 h. (C) The RLuc8 plasmids were used to measure the rates of fusion for FL1 mutants over 120 min. The same phenotypes as those for the 8-h time course are seen over 2 h. (D) The DSP plasmids were used to measure the rates of fusion for FL2 mutants over 8 h. (E) The RLuc8 plasmids were used to measure the rates of fusion for FL2 mutants over 120 min. For panels B and D, luminescence values we normalized to the 8th-hour reading for the WT. For panels C and E, luminescence values were normalized to the 2-h reading for the WT.