The N-terminal Domain of PILB from Neisseria meningitidis Is a Disulfide Reductase That Can Recycle Methionine Sulfoxide Reductases

Abstract

The PilB protein of the Neisseria genus comprises three domains. Two forms have been recently reported to be produced in vivo. One form, containing the three domains, is secreted from the bacterial cytoplasm to the outer membrane, whereas the second form, which is cytoplasmic, only contains the central and the C-terminal domains. The secreted form was shown to be involved in survival under oxidative conditions. Although previous studies indicated that the central and the Cterminal domains display methionine sulfoxide reductase A and B activities, respectively, no function was described so far for the N-terminal domain. In the present study, the N-terminal domain of the PilB of Neisseria meningitidis was produced as a folded entity, and its biochemical and enzymatic properties have been determined. The data show that the N-terminal domain possesses a disulfide redox-active site with a redox potential in the range of that of thioredoxin. Moreover, the N-terminal domain, either as an isolated form or included in PilB, recycles the oxidized forms of the methionine sulfoxide reductases like thioredoxin. These results, which show that the N-terminal domain exhibits a disulfide reductase activity and probably has a thioredoxin-fold, are discussed in relation to its possible functional role in Neisseria.

Ecf, an Alternative Sigma Factor from Neisseria gonorrhoeae , Controls Expression of msrAB , Which Encodes Methionine Sulfoxide Reductase

“…The carboxy-terminal domain possesses MsrB methionine sulfoxide reductase activity specific for the R isomer of methionine sulfoxide, and a central domain has the complementary MsrA activity with specificity for the S isomer (16). The amino-terminal domain contains a signal sequence and possesses a disulfide reductase activity that can recycle methionine sulfoxide reductases (30). This activity allows recycling of MsrA and MsrB activity in the periplasm, a task usually performed by thioredoxin in other species where methionine sulfoxide reductases are cytoplasmic (6).…”

The Thioredoxin Domain of Neisseria gonorrhoeae PilB Can Use Electrons from DsbD to Reduce Downstream Methionine Sulfoxide Reductases

“…The recombinant NT domain from N. meningitidis has been shown to reduce the individual, oxidized MsrA and MsrB domains similar to eTrx (3). A unique surface loop near the active site was identified (13).…”

“…Like many other proteins with a Trx fold, the NT domain presents a Trp-Cys-Xaa-Xaa-Cys catalytic motif that undergoes oxidation-reduction cycling. The redox potential of this motif (Ϫ227 to Ϫ232 mV) from N. meningitidis PilB is slightly more oxidizing than the redox potential of Escherichia coli Trx (eTrx, Ϫ270 mV) (3).…”

“…The PilB proteins (also known as the MsrA/B polyprotein) are composed of three domains. The N-terminal (NT) 3 domain functions as a thioredoxin-like disulfide reductase (3). The middle methionine sulfoxide reductase A (MsrA) and C-terminal methionine sulfoxide reductase B (MsrB) domains function with opposite substrate stereospecificity (2,4,5).…”

The Arabidopsis Plastidic Methionine Sulfoxide Reductase B Proteins. Sequence and Activity Characteristics, Comparison of the Expression with Plastidic Methionine Sulfoxide Reductase A, and Induction by Photooxidative Stress

“…It is noteworthy that MsrB proteins do not display any sequence or structural homology with MsrA. In Neisseria gonorrhoeae, the protein PILB is composed of three subdomains, a domain with thioredoxin-like activity in the N terminus, a domain displaying MsrA activity, and the last one strikingly similar to human SelX, a selenoprotein that exhibits MsrB activity (Olry et al, 2002;Wu et al, 2005). Selenoproteins contain the rare amino acid selenocysteine instead of Cys.…”