Bacterial protein translocase: a unique molecular machine with an army of substrates.
Secretion of most polypeptides across the bacterial plasma membrane is catalyzed by the Sec protein translocase. This complex molecular machine comprises a flexible transmembrane conduit coupled to a motor-like component and displays four activities: (a) it is a specific receptor at its cytoplasmic side for all secretory polypeptides, (b) it converts metabolic energy from ATP and proton gradients into mechanical motion, (c) it prevents substrates from folding in statu translocanti and (d) it binds and releases short segments of the polymeric substrate sequentially. Combination of these activities allows translocase to move processively along the length of the substrate. Substrates are thus gradually expelled from the membrane and are released for subsequent extracytoplasmic folding.
Economou
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Institute of Molecular Biology and Biotechnology-FORTH and Department of Biology, University of Crete, P.O. Box 1527, Crete GR-711 10, Iraklio, Greece. aeconomo@imbb.forth.gr
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D001419:Bacteria / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D013379:Substrate Specificity
D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins