title: Salt sensitivity of minimal twin arginine translocases.
abstract: Bacterial twin arginine translocation (Tat) pathways have evolved to facilitate transport of folded proteins across membranes. Gram-negative bacteria contain a TatABC translocase composed of three subunits named TatA, TatB, and TatC. In contrast, the Tat translocases of most Gram-positive bacteria consist of only TatA and TatC subunits. In these minimal TatAC translocases, a bifunctional TatA subunit fulfils the roles of both TatA and TatB. Here we have probed the importance of conserved residues in the bifunctional TatAy subunit of Bacillus subtilis by site-specific mutagenesis. A set of engineered TatAy proteins with mutations in the cytoplasmic hinge and amphipathic helix regions were found to be inactive in protein translocation under standard growth conditions for B. subtilis or when heterologously expressed in Escherichia coli. Nevertheless, these mutated TatAy proteins did assemble into TatAy and TatAyCy complexes, and they facilitated membrane association of twin arginine precursor proteins in E. coli. Interestingly, most of the mutated TatAyCy translocases were salt-sensitive in B. subtilis. Similarly, the TatAC translocases of Bacillus cereus and Staphylococcus aureus were salt-sensitive when expressed in B. subtilis. Taken together, our present observations imply that salt-sensitive electrostatic interactions have critical roles in the preprotein translocation activity of certain TatAC type translocases from Gram-positive bacteria.
authors: Department of Medical Microbiology, University Medical Center Groningen and University of Groningen, 9700 RB Groningen, The Netherlands.
authors: René
authors: R
authors: van der Ploeg
authors: School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom.
authors: James P
authors: JP
authors: Barnett
authors: School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom.
authors: Nishi
authors: N
authors: Vasisht
authors: Department of Medical Microbiology, University Medical Center Groningen and University of Groningen, 9700 RB Groningen, The Netherlands.
authors: Vivianne J
authors: VJ
authors: Goosens
authors: Department of Medical Microbiology, University Medical Center Groningen and University of Groningen, 9700 RB Groningen, The Netherlands.
authors: Dierk C
authors: DC
authors: Pöther
authors: School of Life Sciences, University of Warwick, Coventry, CV4 7AL, United Kingdom.
authors: Colin
authors: C
authors: Robinson
authors: Department of Medical Microbiology, University Medical Center Groningen and University of Groningen, 9700 RB Groningen, The Netherlands. Electronic address: J.M.van.Dijl@med.umcg.nl.
authors: Jan Maarten
authors: JM
authors: van Dijl
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001120:Arginine / Q000737:chemistry; D001409:Bacillus cereus / Q000378:metabolism; D001412:Bacillus subtilis / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000378:metabolism*; D005816:Genetic Complementation Test; D008089:Listeria monocytogenes / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D012492:Salts / Q000737:chemistry*; D013210:Staphylococcus / Q000378:metabolism; D013211:Staphylococcus aureus / Q000378:metabolism; D055672:Static Electricity
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D026901:Membrane Transport Proteins; D012492:Salts; C499697:TatA protein, E coli; C461379:TatC protein, E coli; D001120:Arginine