Fig. 3: Cryo-EM structure of CpaFADP.
From: Bidirectional pilus processing in the Tad pilus system motor CpaF
A Model of the C2 symmetric CpaF hexamer where all subunits bind ADP/Mg2+. B Superposition of the three distinct NTD2/CTDn+1 units within CpaFADP show close similarity. C Comparison of CpaF asymmetric units in various nucleotide states. (Left) CpaFADP superposed with CpaFAMPPNP. (Right) CpaFADP superposed with CpaFAPO where no nucleotide was observed in the active sites. Zoom box highlights the conformational change in the open state subunit induced by Hinge 2 straightening resulting in rotation of the NTD2 (and NTD1) towards the neighbouring closed subunit. In all superpositions ligands were omitted for clarity. D Analysis of open, closed and open’ active site states with ADP/Mg2+ universally bound. Surface rendering (top row) shows electrostatic charge where blue to red spectrum represent positive to negative charges with units kBT/ec. For clarity, ASP Box E312 has been omitted as well as the distances between E357 and the nucleotide terminal phosphate (bottom row). Both residues with respective distances are shown in Supplementary Fig. 5.
