title: The twin-arginine translocation (Tat) systems from Bacillus subtilis display a conserved mode of complex organization and similar substrate recognition requirements.
abstract: The twin arginine translocation (Tat) system transports folded proteins across the bacterial plasma membrane. In Gram-negative bacteria, membrane-bound TatABC subunits are all essential for activity, whereas Gram-positive bacteria usually contain only TatAC subunits. In Bacillus subtilis, two TatAC-type systems, TatAdCd and TatAyCy, operate in parallel with different substrate specificities. Here, we show that they recognize similar signal peptide determinants. Both systems translocate green fluorescent protein fused to three distinct Escherichia coli Tat signal peptides, namely DmsA, AmiA and MdoD, and mutagenesis of the DmsA signal peptide confirmed that both Tat pathways recognize similar targeting determinants within Tat signals. Although another E. coli Tat substrate, trimethylamine N-oxide reductase, was translocated by TatAdCd but not by TatAyCy, we conclude that these systems are not predisposed to recognize only specific Tat signal peptides, as suggested by their narrow substrate specificities in B. subtilis. We also analysed complexes involved in the second Tat pathway in B. subtilis, TatAyCy. This revealed a discrete TatAyCy complex together with a separate, homogeneous, approximately 200 kDa TatAy complex. The latter complex differs significantly from the corresponding E. coli TatA complexes, pointing to major structural differences between Tat complexes from Gram-negative and Gram-positive organisms. Like TatAd, TatAy is also detectable in the form of massive cytosolic complexes.
authors.affiliation: Department of Biological Sciences, University of Warwick, Coventry, UK.
authors.forename: James P
authors.initials: JP
authors.lastname: Barnett
authors.forename: René
authors.initials: R
authors.lastname: van der Ploeg
authors.forename: Robyn T
authors.initials: RT
authors.lastname: Eijlander
authors.forename: Anja
authors.initials: A
authors.lastname: Nenninger
authors.forename: Sharon
authors.initials: S
authors.lastname: Mendel
authors.forename: Rense
authors.initials: R
authors.lastname: Rozeboom
authors.forename: Oscar P
authors.initials: OP
authors.lastname: Kuipers
authors.forename: Jan Maarten
authors.initials: JM
authors.lastname: van Dijl
authors.forename: Colin
authors.initials: C
authors.lastname: Robinson
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001412:Bacillus subtilis / Q000235:genetics* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D017124:Conserved Sequence; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D015696:Gene Products, tat / Q000378:metabolism*; D017930:Genes, Reporter; D006090:Gram-Negative Bacteria / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D021381:Protein Transport; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D015696:Gene Products, tat; D000255:Adenosine Triphosphate; D010089:Oxidoreductases, N-Demethylating; C023186:trimethylamine dehydrogenase