title: Co-factor insertion and disulfide bond requirements for twin-arginine translocase-dependent export of the Bacillus subtilis Rieske protein QcrA.
abstract: The twin-arginine translocation (Tat) pathway can transport folded and co-factor-containing cargo proteins over bacterial cytoplasmic membranes. Functional Tat machinery components, a folded state of the cargo protein and correct co-factor insertion in the cargo protein are generally considered as prerequisites for successful translocation. The present studies were aimed at a dissection of these requirements with regard to the Rieske iron-sulfur protein QcrA of Bacillus subtilis. Notably, QcrA is a component of the cytochrome bc1 complex, which is conserved from bacteria to man. Single amino acid substitutions were introduced into the Rieske domain of QcrA to prevent either co-factor binding or disulfide bond formation. Both types of mutations precluded QcrA translocation. Importantly, a proofreading hierarchy was uncovered, where a QcrA mutant defective in disulfide bonding was quickly degraded, whereas mutant QcrA proteins defective in co-factor binding accumulated in the cytoplasm and membrane. Altogether, these are the first studies on Tat-dependent protein translocation where both oxidative folding and co-factor attachment have been addressed in a single native molecule.
authors.affiliation: From the Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Hanzeplein 1, P. O. Box 30001, 9700 RB, Groningen, The Netherlands.
authors.forename: Vivianne J
authors.initials: VJ
authors.lastname: Goosens
authors.forename: Carmine G
authors.initials: CG
authors.lastname: Monteferrante
authors.forename: Jan Maarten
authors.initials: JM
authors.lastname: van Dijl
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology* / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D014450:Electron Transport Complex III / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017434:Protein Structure, Tertiary; D021381:Protein Transport / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; C037989:Rieske iron-sulfur protein; D014450:Electron Transport Complex III
keywords: Bacillus; Cytochromes; Disulfide; Iron-Sulfur Protein; Protein Translocation; QcrA; Rieske Protein; TatAy; Twin-arginine Translocation