title: Assembly of the translocase motor onto the preprotein-conducting channel.
abstract: Bacterial protein secretion is catalysed by the SecYEG protein-conducting channel complexed with the SecA ATPase motor. To gain insight into the SecA-SecYEG interaction we used peptide arrays, thermodynamic quantification, mutagenesis and functional assays. Our data reveal that: (i) SecA binds with low affinity on several, peripheral, exposed SecYEG sites. This largely electrostatic association is modulated by temperature and nucleotides. (ii) Binding sites cluster in five major binding 'regions': three that are exclusively cytoplasmic and two that reach the periplasm. (iii) Both the N-terminal and c-terminal regions of SecA participate in binding interactions and share some sites. (iv) Several of these sites are essential for translocase catalysis. Our data provide residue-level dissection of the SecYEG-SecA interaction. Two models of assembly of SecA on dimeric SecYEG are discussed.
authors.affiliation: Institute of Molecular Biology and Biotechnology-FoRTH, PO Box 1385, Iraklio, Crete, Greece.
authors.forename: Spyridoula
authors.initials: S
authors.lastname: Karamanou
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Bariami
authors.forename: Efrosyni
authors.initials: E
authors.lastname: Papanikou
authors.forename: Charalampos G
authors.initials: CG
authors.lastname: Kalodimos
authors.forename: Anastassios
authors.initials: A
authors.lastname: Economou