Fig. 6: Analysis of TadD and its binding interface with RcpA.
From: Assembly mechanism of a Tad secretion system secretin-pilotin complex
a TadD comprises five tetratricopeptide repeats (H1-H10). Zoom box shows how C-terminal RcpA residues 412–416 with associated TadDFRmap (grey) bind TadD within its central groove. b TadD surface rendered to show evolutionary conservation of amino acids. Maroon to green spectrum represents high to variable conservation levels. c TadD surface rendered to show electrostatic charge. Blue to red spectrum represent positive to negative charges with units kBT/ec. d Packing arrangement of TadD subunits around the RcpA secretin. Zoom boxes showcase the disulphide bond formation between C29 and C97 which stabilises Loop 1 (left) and the interface between neighbouring TadD subunits (right). e Structure of P. aeruginosa type 4 pilus system PilF comprising 13 helices. Helix 7 E145 (magenta) located in a similar position to TadD D139 may not mediate PilQ binding23. f C-alpha main chain superposition of TadD and P. aeruginosa PilF with RMSD 3.1 Å calculated using common helices H1-H10.
