title: Genetic evidence for a TatC dimer at the core of the Escherichia coli twin arginine (Tat) protein translocase.
abstract: The twin arginine protein transport (Tat) system transports folded proteins across the cytoplasmic membranes of prokaryotes and the thylakoid membranes of plant chloroplasts. In Escherichia coli, the TatB and TatC components form a multivalent receptor complex that binds Tat substrates. Here, we have used a genetic fusion approach to construct covalent TatC oligomers in order to probe the organisation of TatC. A fused dimer of TatC supported Tat transport activity and was fully stable in vivo. Inactivating point mutations in one or other of the TatC units in the fused TatC dimer did not inactivate TatC function, indicating that only one TatC protomer in the TatC fused dimer needs to be active. Larger covalent fusions of TatC also supported Tat transport activity but were degraded in vivo to release smaller TatC forms. Taken together, these results strongly suggest that TatC forms a functional dimer, and support the idea that there is an even number of TatC protomers in the TatBC complex.
authors.affiliation: Division of Molecular Microbiology, College of Life Sciences, University of Dundee, UK.
authors.forename: Barbara
authors.initials: B
authors.lastname: Maldonado
authors.forename: Grant
authors.initials: G
authors.lastname: Buchanan
authors.forename: Matthias
authors.initials: M
authors.lastname: Müller
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
mesh_terms: D002462:Cell Membrane / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation; D010458:Peptidyl Transferases / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D055503:Protein Multimerization; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; C473116:TatB protein, E coli; C461379:TatC protein, E coli; D010458:Peptidyl Transferases