title: A Tat ménage à trois--The role of Bacillus subtilis TatAc in twin-arginine protein translocation.
abstract: The twin-arginine translocation system (Tat) is a protein transport system that moves fully folded and cofactor-containing proteins across membranes of bacteria, archaea and thylakoids. The minimal Tat pathway is composed of two subunits, TatA and TatC. In some organisms TatA has been duplicated and evolved to form a third specialized subunit, TatB. The Bacillus subtilis genome encodes two TatC subunits (TatCd and TatCy) and three TatA subunits (TatAd, TatAy and TatAc). These subunits combine to form two parallel minimal pathways, TatAy-TatCy and TatAd-TatCd. The purpose and role of the third TatA component, TatAc, has remained ambiguous. In this study we examined the translocation of two natively expressed TatAy-TatCy-dependent substrates, EfeB and QcrA, in various Tat-deficient genetic backgrounds. More specifically, we examined the ability of different mutated TatAy subunits to complement for the absence of wild-type TatAy. We further detailed a graded growth phenotype associated with the functional translocation of EfeB. We found that in various instances where specific amino acid substitutions were made in TatAy, a definite TatAc-associated growth phenotype occurred in genetic backgrounds lacking TatAc. Altogether, our findings show that TatAy and TatAc interact and that this TatAy-TatAc interaction, although not essential, supports the translocation of the Tat substrate EfeB when TatAy function is compromised. This implies that the third TatA-like protein in B. subtilis could represent an intermediate evolutionary step in TatA-TatB specialization.
authors.affiliation: Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, P.O. Box 30001, 9700 RB Groningen, The Netherlands. Electronic address: v.goosens@imperial.ac.uk.
authors.forename: Vivianne J
authors.initials: VJ
authors.lastname: Goosens
authors.affiliation: INRA, UMR1319 Micalis, Jouy-en-Josas, France. Electronic address: adesaneusta@jouy.inra.fr.
authors.forename: Alba
authors.initials: A
authors.lastname: De-San-Eustaquio-Campillo
authors.affiliation: INRA, UMR1319 Micalis, Jouy-en-Josas, France. Electronic address: rut.carballido-lopez@jouy.inra.fr.
authors.forename: Rut
authors.initials: R
authors.lastname: Carballido-López
authors.affiliation: INRA, UMR1319 Micalis, Jouy-en-Josas, France. Electronic address: j.m.van.dijl01@umcg.nl.
authors.forename: Jan Maarten
authors.initials: JM
authors.lastname: van Dijl
mesh_terms: D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins
keywords: Bacillus subtilis; EfeB; TatA; TatAc; TatB; Twin-arginine translocation