Fig. 3.

Completed primosome formation by the addition of gp61 or an alternative, direct formation of the gp41/gp61 primosome. The fluorescence from individual molecules of fDNA with the proteins bound in the order as indicated at the side of each row. (A) The gp32 and gp59 proteins are unlabeled, the gp41 protein is labeled with A488 (gp41^D), and the gp61 protein is labeled with A555 (gp61^A) in the presence of 500 μM MgATP. (B) The gp41 protein is labeled with A488 (gp41^D), and the gp61 protein is labeled with A555 (gp61^A) in the absence of MgATP. The filter sets are described in the legend to Fig. 1.