The outer membrane localization of the Neisseria gonorrhoeae MsrA/B is involved in survival against reactive oxygen species

Abstract

The PilB protein of Neisseria gonorrhoeae has been reported to be involved in the regulation of pilin gene transcription, but it also possesses significant homology to the peptide methionine sulfoxide reductase family of enzymes, specifically MsrA and MsrB from Escherichia coli. MsrA and MsrB in E. coli are able to reduce methionine sulfoxide residues in proteins to methionines. In addition, the gonococcal PilB protein encodes for both MsrA and MsrB activity associated with the repair of oxidative damage to proteins. In this work, we demonstrate that the PilB protein of Neisseria gonorrhoeae is not involved in pilus expression. Additionally, we show that wild-type N. gonorrhoeae produces two forms of this polypeptide, one of which contains a signal sequence and is secreted from the bacterial cytoplasm to the outer membrane; the other lacks a signal sequence and is cytoplasmic. Furthermore, we show that the secreted form of the PilB protein is involved in survival in the presence of oxidative damage.

Contribution of the stereospecific methionine sulphoxide reductases MsrA and MsrB to oxidative and nitrosative stress resistance in the food-borne pathogen Campylobacter jejuni

“…Neither protein appears to have an obvious signal sequence, which is also consistent with a function in the cytoplasm, although this needs to be confirmed experimentally. There is evidence that some Msr enzymes may be extracytoplasmic, such as the secreted form of PilB in N. gonorrhoeae (Skaar et al, 2002). In addition to MsrA and MsrB, there is emerging evidence that many bacteria may also contain additional, unrelated enzymes with Met-SO reductase activity, exemplified by the YebR protein of E. coli (Lin et al, 2007).…”

“…The effects do not appear to be cumulative, with the amount of killing of the double mutant being the same as for the two single mutants, implying that the loss of either Msr activity is a significant detriment to the cell. Sensitivity to peroxide is seen in msrA and msrB mutants in N. gonorrhoeae (Skaar et al, 2002), H. pylori (Alamuri & Maier, 2004) and X. campestris (Vattanaviboon et al, 2005). In C. jejuni, however, when hydrogen peroxide was used in cell viability (kill curve) assays only the msrA/B double mutant was significantly affected.…”

“…Superoxide dismutase of C. jejuni has been studied (Purdy & Park, 1994;Purdy et al, 1999), but presumably this activity is not sufficient to prevent superoxide-mediated oxidation of methionine residues to such a degree as to cause the mutant phenotypes seen here. Mutants in a range of other bacteria lacking Msr activity, such as X. campestris (Vattanaviboon et al, 2005), N. gonnorhoeae (Skaar et al, 2002) and H. pylori (Alamuri & Maier, 2004), have been shown to be more sensitive to superoxide stress. However, it is thought that superoxide does not oxidize methionine residues directly, but rather does so through dismutation to hydrogen peroxide (carried out by metal ions) and through formation of the hydroxyl radical HO .…”

“…The oxidation of methionine residues by toxic oxygen intermediates is a major source of oxidative damage in cells . Formation of methionine sulphoxide (Met-SO) can lead to protein conformational changes, causing inactivation (Skaar et al, 2002). Removal of methionine from the N terminus of many newly synthesized proteins is essential for folding and activity.…”

“…The importance of Msr activity has been demonstrated experimentally in several eukaryotes and a few bacteria, including Escherichia coli (St John et al, 2001;Grimaud et al, 2001), Staphylococcus aureus (Moskovitz et al, 2002), Xanthomonas campestris (Vattanaviboon et al, 2005), Mycobacterium smegmatis (Douglas et al, 2004), Lactobacillus reuteri (Walter et al, 2005), Helicobacter pylori (Alamuri & Maier, 2004) and Neisseria gonorrhoeae (Skaar et al, 2002). Where studied, Msr activity seems to be required for full resistance to oxidative and nitrosative stress agents and, where investigated in the case of pathogens, for colonization and virulence.…”