Figure 4.

Superposition of YdiV–FlhD structure and FlhD₄C₂ structure. The structure of FlhD₄C₂ is used as a model, and YdiV–FlhD is superimposed to the third and the fourth FlhD molecules of FlhD₄C₂, respectively (YdiV: hotpink, FlhC: yellow, FlhD: blue). Whole structures are shown in cartoon mode and residues of FlhC involved in mutation studies are shown in sticks. The right figure presents a close-up view of interface between the second and the third FlhD molecules of FlhD₄C₂. The α1 and α4 of the third FlhD mediate both the YdiV–FlhD interaction and the second–third FlhD interaction. Two interfaces are overlapped, and the interface of YdiV–FlhD seems more solid than D2–D3. Helices from FlhD are marked in white color and the ones from YdiV in black.