Journal
JOURNAL OF BACTERIOLOGY
Volume 188, Issue 16, Pages 5839-5850Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/JB.00430-06
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Funding
- NIDDK NIH HHS [DK062852, DK60061, R01 DK062852, R01 DK060061] Funding Source: Medline
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The reductive repair of oxidized methionine residues performed by methionine sulfoxide reductase is important for the gastric pathogen Helicobacter pylori to maintain persistent stomach colonization. Methionine-containing proteins that are targeted for repair by Msr were identified from whole-cell extracts (after cells were exposed to O-2 stress) by using a coimmunoprecipitation approach. Proteins identified as Msr-interacting included catalase, GroEL, thioredoxin-1 (Trx1), and site-specific recombinase; with one exception (Trx1, the reductant for Msr) all these proteins have approximately twofold higher methionine (Met) content than other proteins. These Met-rich proteins were purified and were shown to individually form a cross-linked adduct with Msr. Catalase-specific activity in an msr strain was one-half that of the parent strain; this difference was only observed under oxidative stress conditions, and the activity was restored to nearly wild-type levels by adding Msr plus dithiothreitol to msr strain extracts. In agreement with the cross-linking study, pure Msr used Trx1 but not Trx2 as a reductant. Comparative structure modeling classified the H. pylori Msr in class II within the MsrB family, like the Neisseria enzymes. Pure H. pylori enzyme reduced only the R isomer of methyl p-tolyl-sulfoxide with an apparent K-m of 4.1 mM for the substrate. Stress conditions (peroxide, peroxynitrite, and iron starvation) all caused approximately 3- to 3.5-fold transcriptional up-regulation of msr. Neither the O-2 level during growth nor the use of background regulatory mutants had a significant effect on msr transcription. Late log and stationary phase cultures had the highest Msr protein levels and specific activity.
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