Disulfide oxidoreductase activity of Shigella flexneri is required for release of Ipa proteins and invasion of epithelial cells.
0301 basic medicine
Antigens, Bacterial
0303 health sciences
Base Sequence
Genotype
Molecular Sequence Data
Protein Disulfide-Isomerases
Apoptosis
Epithelium
Cell Line
3. Good health
Kinetics
03 medical and health sciences
Bacterial Proteins
Oligodeoxyribonucleotides
Genes, Bacterial
Mutagenesis, Site-Directed
Animals
Point Mutation
Cysteine
Disulfides
Isomerases
Oxidation-Reduction
Bacterial Outer Membrane Proteins
DOI:
10.1073/pnas.92.11.4927
Publication Date:
2006-05-31T13:11:38Z
AUTHORS (4)
ABSTRACT
Secretion of IpaB, IpaC, and IpaD proteins of Shigella flexneri, essential for the invasion of epithelial cells, requires a number of proteins encoded by the spa and mxi loci on the large plasmid. Introduction of dsbA::Tn5 into S.flexneri from Escherichia coli K-12 reduced invasiveness, which resulted from a decrease in the capacity to release IpaB, IpaC, and IpaD proteins into the external medium. Examination of the surface-presented Ipa proteins of the dsbA mutant, however, revealed Ipa proteins at levels similar to those on wild-type cells. Since the defective phenotype was similar to that of the spa32 mutant of S. flexneri and the Spa32 sequence possessed two Cys residues, the effect of dsbA mutation of the folding structure of Spa32 under reducing conditions and on the surface expression of Spa32 was investigated. The results indicated that Spa32 was a disulfide-containing protein whose correctly folded structure was required for its presentation on the outer membrane. Indeed, replacing either one of the two Cys residues in Spa32 with Ser by site-directed mutagenesis reduced its capacity to release Ipa proteins into the external medium and led to the accumulation of Spa32 protein in the periplasm. These results indicated that the DsbA protein performs an essential function during the invasion of mammalian cells, by facilitating transport of the Spa32 protein across the outer membrane.
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