Characterization of SrgA, a Salmonella enterica serovar Typhimurium virulence plasmid-encoded paralogue of the disulfide oxidoreductase DsbA, essential for biogenesis of plasmid-encoded fimbriae

C W Bouwman; M Kohli; A Killoran; G A Touchie; R J Kadner; N L Martin

doi:10.1128/JB.185.3.991-1000.2003

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Characterization of SrgA, a Salmonella enterica serovar Typhimurium virulence plasmid-encoded paralogue of the disulfide oxidoreductase DsbA, essential for biogenesis of plasmid-encoded fimbriae

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Characterization of SrgA, a Salmonella enterica serovar Typhimurium virulence plasmid-encoded paralogue of the disulfide oxidoreductase DsbA, essential for biogenesis of plasmid-encoded fimbriae

C W Bouwman, M Kohli, A Killoran, G A Touchie, R J Kadner and N L Martin

Journal of bacteriology, Vol.185(3), pp.991-1000

02/2003

DOI: 10.1128/JB.185.3.991-1000.2003

PMCID: PMC142830

PMID: 12533475

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Abstract

Disulfide oxidoreductases are viewed as foldases that help to maintain proteins on productive folding pathways by enhancing the rate of protein folding through the catalytic incorporation of disulfide bonds. SrgA, encoded on the virulence plasmid pStSR100 of Salmonella enterica serovar Typhimurium and located downstream of the plasmid-borne fimbrial operon, is a disulfide oxidoreductase. Sequence analysis indicates that SrgA is similar to DsbA from, for example, Escherichia coli, but not as highly conserved as most of the chromosomally encoded disulfide oxidoreductases from members of the family Enterobacteriaceae. SrgA is localized to the periplasm, and its disulfide oxidoreductase activity is dependent upon the presence of functional DsbB, the protein that is also responsible for reoxidation of the major disulfide oxidoreductase, DsbA. A quantitative analysis of the disulfide oxidoreductase activity of SrgA showed that SrgA was less efficient than DsbA at introducing disulfide bonds into the substrate alkaline phosphatase, suggesting that SrgA is more substrate specific than DsbA. It was also demonstrated that the disulfide oxidoreductase activity of SrgA is necessary for the production of plasmid-encoded fimbriae. The major structural subunit of the plasmid-encoded fimbriae, PefA, contains a disulfide bond that must be oxidized in order for PefA stability to be maintained and for plasmid-encoded fimbriae to be assembled. SrgA efficiently oxidizes the disulfide bond of PefA, while the S. enterica serovar Typhimurium chromosomally encoded disulfide oxidoreductase DsbA does not. pefA and srgA were also specifically expressed at pH 5.1 but not at pH 7.0, suggesting that the regulatory mechanisms involved in pef gene expression are also involved in srgA expression. SrgA therefore appears to be a substrate-specific disulfide oxidoreductase, thus explaining the requirement for an additional catalyst of disulfide bond formation in addition to DsbA of S. enterica serovar Typhimurium.

Disulfides - metabolism

Amino Acid Sequence

Flagella - physiology

Oxidation-Reduction

Salmonella typhimurium - genetics

Salmonella typhimurium - pathogenicity

Open Reading Frames

Molecular Sequence Data

Oxidoreductases - physiology

Protein Disulfide-Isomerases - genetics

Virulence - genetics

Fimbriae, Bacterial - physiology

Plasmids

Salmonella typhimurium - enzymology

Protein Disulfide-Isomerases - physiology

Details

Title: Subtitle: Characterization of SrgA, a Salmonella enterica serovar Typhimurium virulence plasmid-encoded paralogue of the disulfide oxidoreductase DsbA, essential for biogenesis of plasmid-encoded fimbriae
Creators: C W Bouwman - Department of Microbiology and Immunology, Queen's University, Kingston, Ontario, Canada K7L 3N6
M Kohli
A Killoran
G A Touchie
R J Kadner
N L Martin
Resource Type: Journal article
Publication Details: Journal of bacteriology, Vol.185(3), pp.991-1000
DOI: 10.1128/JB.185.3.991-1000.2003
PMID: 12533475
PMCID: PMC142830
NLM abbreviation: J Bacteriol
ISSN: 0021-9193
eISSN: 1098-5530
Publisher: United States
Grant note: F32 GM019078 / NIGMS NIH HHS R01 GM019078 / NIGMS NIH HHS GM 19078 / NIGMS NIH HHS
Language: English
Date published: 02/2003
Academic Unit: Neurology; Psychiatry
Record Identifier: 9984020998402771

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