Figure 7.. EM images of the wild-type and mutant SsoRadA proteins. Negative staining EM images of SsoRadA wild-type, R83A, N85P, R83E and F73D proteins in the presence of AMP-PNP, Mg2+ and a ssDNA substrate (872 nucleotides in length). The results indicate that wild-type, R83A, N85P and R83E proteins are capable of forming filamentous structures. The wild-type (left-top panel) and N85P (left-middle panel) protein filaments often exhibited right-handed helices. In contrast, left-handed helices were often observed in the R83A protein filaments (right-top and right-middle panels). R83E proteins form filamentous structures with different lengths (left-bottom panel). The F73D point mutant proteins, defective in protein polymerization, form only protein aggregates with irregular morphology (right-bottom panel). Right- and left-handed helices are marked using white arrows.