Characterization of DsbD in Neisseria meningitidis

• Authors: Pradeep Kumar, Emory University; Soma Sannigrahi, Emory University; Jessica Scoullar, University of Western Australia; Charlene M. Kahler, University of Western Australia; Yih-Ling Tzeng, Emory University
• Journal Title: Molecular Microbiology
• Volume: Volume 79, Number 6
• Publisher: Wiley: 12 months | 2011-03, Pages 1557-1573
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1111/j.1365-2958.2011.07546.x
• Subjects: Biology, Microbiology
• Keywords: Neisseria meningitidis; DsbD; MisRS; two-component regulatory system; DsbA

Abstract

Proper periplasmic disulfide bond formation is important for folding and stability of many secreted and membrane proteins, and is catalyzed by three DsbA oxidoreductases in Neisseria meningitidis. DsbD provides reducing power to DsbC that shuffles incorrect disulfide bond in misfolded proteins as well as to the periplasmic enzymes that reduce apo-cytochrome c (CcsX) or repair oxidative protein damages (MrsAB). The expression of dsbD, but not other dsb genes, is positively regulated by the MisR/S two-component system. qRT-PCR analyses showed significantly reduced dsbD expression in all misR/S mutants, which was rescued by genetic complementation. The direct and specific interaction of MisR with the upstream region of the dsbD promoter was demonstrated by EMSA, and the MisR-binding sequences were mapped. Further, the expression of dsbD was found to be induced by dithiothrietol (DTT), through the MisR/S regulatory system. Surprisingly, we revealed that inactivation of dsbD can only be achieved in a strain carrying an ectopically located dsbD, in the dsbA1A2 double mutant or in the dsbA1A2A3 triple mutant, thus DsbD is indispensable for DsbA-catalyzed oxidative protein folding in N. meningitidis. The defects of the meningococcal dsbA1A2 mutant in transformation and resistance to oxidative stress were more severe in the absence of dsbD.