title: Cross-linked SecA dimers are not functional in protein translocation.
abstract: The ATPase SecA is involved in post-translational protein translocation through the SecY channel across the bacterial inner membrane. SecA is a dimer that can dissociate into monomers with translocation activity. Here, we have addressed whether dissociation of the SecA dimer is required for translocation. We show that a dimer in which the two subunits are cross-linked by disulfide bridges is inactive in protein translocation, translocation ATPase, and binding to a lipid bilayer. In contrast, upon reduction of the disulfide bridges, the resulting monomers regain these activities. These data support the notion that dissociation of SecA dimers into monomers occurs during protein translocation.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Eran
authors.initials: E
authors.lastname: Or
authors.forename: Tom
authors.initials: T
authors.lastname: Rapoport
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003432:Cross-Linking Reagents / Q000737:chemistry; D003958:Diamide / Q000494:pharmacology; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D004229:Dithiothreitol / Q000494:pharmacology; D029968:Escherichia coli Proteins / Q000378:metabolism; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D010084:Oxidation-Reduction; D011498:Protein Precursors / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D000069816:SEC Translocation Channels; D000081416:SecA Proteins
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D004220:Disulfides; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D050505:Mutant Proteins; D011498:Protein Precursors; D000069816:SEC Translocation Channels; C057184:outer membrane protein A precursor (E coli); D003958:Diamide; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins; D004229:Dithiothreitol