title: Legionella pneumophila utilizes a single-player disulfide-bond oxidoreductase system to manage disulfide bond formation and isomerization.
abstract: Legionella pneumophila uses a single homodimeric disulfide bond (DSB) oxidoreductase DsbA2 to catalyze extracytoplasmic protein folding and to correct DSB errors through protein-disulfide isomerase (PDI) activity. In Escherichia coli, these functions are separated to avoid futile cycling. In L. pneumophila, DsbA2 is maintained as a mixture of disulfides (S-S) and free thiols (SH), but when expressed in E. coli, only the SH form is observed. We provide evidence to suggest that structural differences in DsbB oxidases (LpDsbB1 and LpDsbB2) and DsbD reductases (LpDsbD1 and LpDsbD2) (compared with E. coli) permit bifunctional activities without creating a futile cycle. LpdsbB1 and LpdsbB2 partially complemented an EcdsbB mutant while neither LpdsbD1 nor LpdsbD2 complemented an EcdsbD mutant unless DsbA2 was also expressed. When the dsb genes of E. coli were replaced with those of L. pneumophila, motility was restored and DsbA2 was present as a mixture of redox forms. A dominant-negative approach to interfere with DsbA2 function in L. pneumophila determined that DSB oxidase activity was necessary for intracellular multiplication and assembly/function of the Dot/Icm Type IVb secretion system. Our studies show that a single-player system may escape the futile cycle trap by limiting transfer of reducing equivalents from LpDsbDs to DsbA2.
authors.affiliation: Department of Medicine, Division of Infectious Diseases & International Health, University of Virginia Health System, Charlottesville, VA, 22901, USA; Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, VA, 22908, USA.
authors.forename: Zegbeh Z
authors.initials: ZZ
authors.lastname: Kpadeh
authors.forename: Shandra R
authors.initials: SR
authors.lastname: Day
authors.forename: Brandy W
authors.initials: BW
authors.lastname: Mills
authors.forename: Paul S
authors.initials: PS
authors.lastname: Hoffman
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004220:Disulfides / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016952:Legionella pneumophila / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; C079503:DsbB protein, Bacteria; D008565:Membrane Proteins; D010088:Oxidoreductases