Fig. 5: Stabilisation of the functional and oligomeric states of CtpA.
a The substrate binding site in an active subunit. The enlarged view shows how the stabilisation of the active state is mediated by the salt bridge between Glu-96 and Arg-162 and the cation–π interaction between Phe-105 and Arg-162 (dotted box). Processive proteolysis of the C-terminus of the substrate is driven by the pronated Arg-162. The cryo-EM density near the C-terminus of the substrate peptide is shown. b The crystal structure of the CtpAF105R mutant, displayed in surface view. The six resting subunits are labelled in cold colours, and one of the subunits is transparent. c The crossing angles of the two α-helices in the C-terminal dimerisation interface of CtpA from P. aeruginosa (left) and H. pylori (right).
