title: Allosteric communication between signal peptides and the SecA protein DEAD motor ATPase domain.
abstract: SecA, the preprotein translocase ATPase is built of an amino-terminal DEAD helicase motor domain bound to a regulatory C-domain. SecA recognizes mature and signal peptide preprotein regions. We now demonstrate that the amino-terminal 263 residues of the ATPase subdomain of the DEAD motor are necessary and sufficient for high affinity signal peptide binding. Binding is abrogated by deletion of residues 219-244 that lie within SSD, a novel substrate specificity element of the ATPase subdomain. SSD is essential for protein translocation, is unique to SecA, and is absent from other DEAD proteins. Signal peptide binding to the DEAD motor is controlled in trans by the C-terminal intramolecular regulator of ATPase (IRA1) switch. IRA1 mutations that activate the DEAD motor ATPase also enhance signal peptide affinity. This mechanism coordinates signal peptide binding with ATPase activation. Signal peptide binding causes widespread conformational changes to the ATPase subdomain and inhibits the DEAD motor ATPase. This involves an allosteric mechanism, since binding occurs at sites that are distinct from the catalytic ATPase determinants. Our data reveal the physical determinants and sophisticated intramolecular regulation that allow signal peptides to act as allosteric effectors of the SecA motor.
authors.affiliation: Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology-Hellas, Department of Biology, University of Crete, P.O. Box 1527, GR-711 10 Iraklio, Crete, Greece.
authors.forename: Catherine
authors.initials: C
authors.lastname: Baud
authors.forename: Spyridoula
authors.initials: S
authors.lastname: Karamanou
authors.forename: Giorgos
authors.initials: G
authors.lastname: Sianidis
authors.forename: Eleftheria
authors.initials: E
authors.lastname: Vrontou
authors.forename: Anastasia S
authors.initials: AS
authors.lastname: Politou
authors.forename: Anastassios
authors.initials: A
authors.lastname: Economou
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000378:metabolism; D000495:Allosteric Site; D001426:Bacterial Proteins; D001665:Binding Sites; D003432:Cross-Linking Reagents / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism; D008957:Models, Genetic; D009154:Mutation; D011485:Protein Binding; D011487:Protein Conformation; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D020349:Surface Plasmon Resonance
chemical_list: D001426:Bacterial Proteins; D003432:Cross-Linking Reagents; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D000069816:SEC Translocation Channels; D000251:Adenosine Triphosphatases; D000081416:SecA Proteins