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

Junzhu Wu,Sandrine Boschi-Muller,Guy Branlant,Fabrice Neiers

doi:10.1074/jbc.m500385200

Junzhu Wu, Sandrine Boschi-Muller + Show 2 more

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https://doi.org/10.1074/jbc.m500385200

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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 C-terminal 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.

Highlights

The obligate human pathogens, Neisseria gonorrhoeae and Neisseria meningitidis are the only two pathogenic members of the Neisseria family of Gram-negative bacteria
The fact that the extracytoplasmic localization of PilB was shown to be required for survival in the presence of oxidative damage raises the question of the function of the N-terminal domain in the periplasm and of its relationship with the MsrA and MsrB activities
In an attempt to identify the role of the N-terminal domain of PilB, a soluble form of the N. meningitidis domain of 143 amino acids, which only differs from its N. gonorrhoeae counterpart by four amino acids, has been overproduced and purified

Summary

Introduction

The obligate human pathogens, Neisseria gonorrhoeae and Neisseria meningitidis are the only two pathogenic members of the Neisseria family of Gram-negative bacteria. N. gonorrhoeae and N. meningitidis possess several antioxidant defense mechanisms among which the PilB protein was recently shown to play an essential role [3]. The second one is a truncated cytoplasmic form corresponding to amino acids 196 –521 and lacks the N-terminal domain. The fact that the extracytoplasmic localization of PilB was shown to be required for survival in the presence of oxidative damage raises the question of the function of the N-terminal domain in the periplasm and of its relationship with the MsrA and MsrB activities. In an attempt to identify the role of the N-terminal domain of PilB, a soluble form of the N. meningitidis domain of 143 amino acids, which only differs from its N. gonorrhoeae counterpart by four amino acids (see Fig. 1), has been overproduced and purified. The results demonstrate that the N-terminal domain displays a disulfide reductase activity that is able to recycle

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