title: Methionine sulfoxide reductase in Helicobacter pylori: interaction with methionine-rich proteins and stress-induced expression.
abstract: 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.
authors.affiliation: Department of Microbiology, The University of Georgia, Biological Sciences Bldg., 527, 1000 Cedar Street, Athens, GA 30602, USA.
authors.forename: Praveen
authors.initials: P
authors.lastname: Alamuri
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Maier
mesh_terms: D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D016480:Helicobacter pylori / Q000201:enzymology*; D008715:Methionine / Q000737:chemistry* / Q000378:metabolism; D051150:Methionine Sulfoxide Reductases; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism*; D011487:Protein Conformation
chemical_list: D008715:Methionine; D010088:Oxidoreductases; D051150:Methionine Sulfoxide Reductases; C027219:methionine sulfoxide reductase