title: Quaternary dynamics of the SecA motor drive translocase catalysis.
abstract: 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 SecYEG as a dimer and becomes functionally asymmetric. Docking occurs via only one protomer. The second protomer allosterically regulates downstream steps. Binding of one preprotein signal peptide to the SecYEG-docked SecA protomer elongates the SecA dimer and triggers the translocase holoenzyme to obtain a lower activation energy conformation. ATP hydrolysis monomerizes the triggered SecA dimer, causing mature chain trapping and processive translocation. This is a unique example of one protein exploiting quaternary dynamics to become a substrate receptor, a "loading clamp," and a "processive motor." This mechanism has widespread implications on protein translocases, chaperones, and motors.
authors: Institute of Molecular Biology and Biotechnology (FORTH), University of Crete, P.O. Box 1385, Iraklio, Crete 71110, Greece.
authors: Giorgos
authors: G
authors: Gouridis
authors: Institute of Molecular Biology and Biotechnology (FORTH), University of Crete, P.O. Box 1385, Iraklio, Crete 71110, Greece; Rega Institute, Department of Microbiology and Immunology, KU Leuven, 3000 Leuven, Belgium.
authors: Spyridoula
authors: S
authors: Karamanou
authors: Institute of Molecular Biology and Biotechnology (FORTH), University of Crete, P.O. Box 1385, Iraklio, Crete 71110, Greece; Department of Biology, University of Crete, P.O. Box 1385, Iraklio, Crete 71110, Greece.
authors: Marios Frantzeskos
authors: MF
authors: Sardis
authors: Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors: Martin Alexander
authors: MA
authors: Schärer
authors: Paul Scherrer Institute, CH-5232 Villigen PSI, Switzerland.
authors: Guido
authors: G
authors: Capitani
authors: Institute of Molecular Biology and Biotechnology (FORTH), University of Crete, P.O. Box 1385, Iraklio, Crete 71110, Greece; Department of Biology, University of Crete, P.O. Box 1385, Iraklio, Crete 71110, Greece; Rega Institute, Department of Microbiology and Immunology, KU Leuven, 3000 Leuven, Belgium. Electronic address: tassos.economou@rega.kuleuven.be.
authors: Anastassios
authors: A
authors: Economou
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D002384:Catalysis; D019281:Dimerization; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D006868:Hydrolysis; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D021122:Protein Subunits; D000069816:SEC Translocation Channels; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins