Fig. 6.

Proposed models of function. a In vivo model of PilT conformations. The entire T4aP is shown with an eye symbol (left) indicating the viewing direction for the model (right). This model suggests that the CCCCCC and OOCOOC conformations are of in vivo functional relevance. b In vitro model of PilT conformations. This model illustrates that in vitro PilT is a mixture of OOCOOC and OCOCOC conformations; added ADP can modestly increase the proportion of the OCOCOC conformation, while added ATP strongly favors the CCCCCC conformation. c Updated model of ATP binding and hydrolysis in PilT. ADP is predicted to be retained at two open interfaces, so only the other two open interfaces are available for binding ATP, promoting a single direction of rotation