Bacterial preprotein translocase: mechanism and conformational dynamics of a processive enzyme.

Quaternary dynamics of the SecA motor drive translocase catalysis.

Most secretory preproteins exit bacterial cells through the protein translocase, comprising the SecYEG channel and the dimeric peripheral ATPase motor SecA. Energetic coupling to work remains elusive. We now demonstrate that translocation is driven by unusually dynamic quaternary changes in SecA. The dimer occupies several successive states with distinct protomer arrangements. SecA docks on Sec...

Reconstitution of purified bacterial preprotein translocase in liposomes.

The SecDFyajC domain of preprotein translocase controls preprotein movement by regulating SecA membrane cycling.

Escherichia coli preprotein translocase comprises a membrane-embedded hexameric complex of SecY, SecE, SecG, SecD, SecF and YajC (SecYEGDFyajC) and the peripheral ATPase SecA. The energy of ATP binding and hydrolysis promotes cycles of membrane insertion and deinsertion of SecA and catalyzes the movement of the preprotein across the membrane. The proton motive force (PMF), though not essential,...

The PrlA and PrlG phenotypes are caused by a loosened association among the translocase SecYEG subunits.

prlA mutations in the gene encoding the SecY subunit of the membrane domain of the Escherichia coli preprotein translocase confer many phenotypes: enhanced translocation rates, increased affinity for SecA, diminished requirement for functional leader sequences, reduced proton-motive force (PMF) dependence of preprotein translocation and facilitated translocation of preproteins with folded domai...

Helicase Motif III in SecA is essential for coupling preprotein binding to translocation ATPase.

The SecA ATPase is a protein translocase motor and a superfamily 2 (SF2) RNA helicase. The ATPase catalytic core ('DEAD motor') contains the seven conserved SF2 motifs. Here, we demonstrate that Motif III is essential for SecA-mediated protein translocation and viability. SecA Motif III mutants can bind ligands (nucleotide, the SecYEG translocase 'channel', signal and mature preprotein domains)...