title: Characterisation of Tat protein transport complexes carrying inactivating mutations.
abstract: The Tat system functions to transport folded proteins across the bacterial cytoplasmic membrane and the thylakoid membrane of plant chloroplasts. Tat transport involves a high molecular weight TatBC-containing complex that transiently associates with TatA during protein translocation. Sedimentation equilibrium experiments were used to determine a protein-only molecular mass for the TatBC complex of 630+/-30kDa, suggesting that it contains approximately 13 copies of the TatB and TatC protomers. Point mutations that inactivate Tat transport have previously been identified in each of TatA, TatB, and TatC. Analysis of the TatBC complexes formed by these inactive variants demonstrates that the amino acid substitutions neither affect the composition of the TatBC complex nor cause accumulation of the assembled TatABC translocation site. In addition, the TatA protein is shown not to be required for the assembly or stability of the TatBC complex.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: McDevitt
authors.forename: Matthew G
authors.initials: MG
authors.lastname: Hicks
authors.forename: Tracy
authors.initials: T
authors.lastname: Palmer
authors.forename: Ben C
authors.initials: BC
authors.lastname: Berks
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001665:Binding Sites; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D013329:Structure-Activity Relationship
chemical_list: D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; C499697:TatA protein, E coli; C473116:TatB protein, E coli; C461379:TatC protein, E coli; C408585:twin-arginine translocase complex, E coli