RRC ID 35197
Author Shimizu T, Kawakami S, Sato T, Sasaki T, Higashide M, Hamabata T, Ohta T, Noda M.
Title The serine 31 residue of the B subunit of Shiga toxin 2 is essential for secretion in enterohemorrhagic Escherichia coli.
Journal Infect Immun
Abstract Shiga toxins produced by enterohemorrhagic Escherichia coli (EHEC) include Shiga toxin 1 (Stx1) as well as Shiga toxin 2 (Stx2). Stx1 is cell associated, whereas Stx2 is localized to the culture supernatant. We have analyzed the secretion of Stx2 by generating histidine-tagged StxB (StxB-H). Although neither StxB1-H nor StxB2-H was secreted in StxB-H-overexpressed EHEC, StxB2-H-overexpressed EHEC showed inhibited Stx2 secretion. On the other hand, StxB1-H-overexpressed EHEC showed no alteration of Stx2 secretion. B-subunit chimeras of Stx1 and Stx2 were used to identify the specific residue of StxB2 that the Stx2 secretory system recognizes. Alteration of the serine 31 residue to an asparagine residue (S31N) in StxB2-H enabled the recovery of Stx2 secretion. On the other hand, alteration of the asparagine 32 residue to a serine residue (N32S) in StxB1-H caused the partial secretion of a point-mutated histidine-tagged B subunit in EHEC. Based on the evidence, it appeared possible that this residue might contain secretion-related information for Stx2 secretion. To investigate this hypothesis, we constructed an isogenic mutant EHEC (Stx1B subunit, N32S) strain and an isogenic mutant EHEC (Stx2B subunit, S31N) strain. Although the mutant Stx2 was cell associated in isogenic mutant EHEC, mutant Stx1 was not extracellular. However, when we used plasmids for the expression of the mutant holotoxins, the overexpressed mutant Stx1 was found in the supernatant fraction, and the overexpressed mutant Stx2 was found in the cell-associated fraction in mutant holotoxin gene-transformed EHEC. These results indicate that the serine 31 residue of the B subunit of Stx2 contains secretion-related information.
Volume 75(5)
Pages 2189-200
Published 2007-5
DOI 10.1128/IAI.01546-06
PII IAI.01546-06
PMID 17325057
PMC PMC1865754
MeSH Animals Escherichia coli Infections / microbiology Escherichia coli Infections / mortality Escherichia coli O157 / genetics Escherichia coli O157 / growth & development Escherichia coli O157 / metabolism* Escherichia coli O157 / pathogenicity* Gene Expression Regulation, Bacterial* Male Mice Models, Molecular Mutation Protein Subunits / chemistry* Protein Subunits / genetics Serine / chemistry* Shiga Toxin 2 / chemistry* Shiga Toxin 2 / genetics Shiga Toxin 2 / metabolism* Shiga Toxin 2 / toxicity
IF 3.16
Times Cited 15
Prokaryotes E. coli ?