Periplasmic Superoxide Dismutase in Meningococcal Pathogenicity

Abstract

Meningococcal sodC encodes periplasmic copper-and zinc-cofactored superoxide dismutase (Cu,Zn SOD) which catalyzes the conversion of the superoxide radical anion to hydrogen peroxide, preventing a sequence of reactions leading to production of toxic hydroxyl free radicals. From its periplasmic location, Cu,Zn SOD was inferred to acquire its substrate from outside the bacterial cell and was speculated to play a role in preserving meningococci from the action of microbicidal oxygen free radicals produced in the context of host defense. A sodC mutant was constructed by allelic exchange and was used to investigate the role of Cu,Zn SOD in pathogenicity. Wild-type and mutant meningococci grew at comparable rates and survived equally long in aerobic liquid culture. The mutant showed no increased sensitivity to paraquat, which generates superoxide within the cytosol, but was approximately 1,000-fold more sensitive to the toxicity of superoxide generated in solution by the xanthine/xanthine oxidase system. These data support a role for meningococcal Cu,Zn SOD in protection against exogenous superoxide. In experiments to translate this into a role in pathogenicity, wild-type and mutant organisms were used in an intraperitoneal mouse infection model. The sodC mutant was significantly less virulent. We conclude that periplasmic Cu,Zn SOD contributes to the virulence of Neisseria meningitidis, most likely by reducing the effectiveness of toxic oxygen host defenses.

Identification and subcellular localization of a novel Cu,Zn superoxide dismutase of Mycobacterium tuberculosis

“…In contrast, the absence of Cu,ZnSOD in C. crescentus had no e¡ect on its sensitivity to paraquat or chlorpromazine [18]. Mutations in Cu,ZnSOD caused elevated sensitivities to the exogenous superoxide in S. typhimurium, N. meningitidis, and H. ducreyi suggesting that the primary role of Cu,ZnSOD was to protect bacteria from the exogenous oxyradicals [20,27,33,34].…”

“…The presence of Cu,ZnSOD in the periplasm of these pathogens could provide a defense mechanism against the hostile environment in the host cells and hence maybe required for virulence [34]. Overexpression of a hydrogen peroxide-resistant periplasmic Cu,ZnSOD protected E. coli from macrophage killing [35] and Cu,ZnSOD mutants of S. typhimurium, N. meningitidis, and H. ducreyi were shown to be less virulent in killing mice infected with the pathogens [20,27,33,34]. By analogy, Cu,ZnSOD of M. tuberculosis may play a similar role in determining virulence.…”

Post-translational processing of Neisseria meningitidis γ-glutamyl aminopeptidase and its association with inner membrane facing to the cytoplasmic space

“…To use the periplasmic meningococcal sodC gene product (SodC) [27] as a periplasmic marker, a N. meningitidis strain with a FLAG epitope-tagged sodC gene was constructed as follows: a 3-kb DNA fragment containing the sodC gene with its 1 kb upper and lower regions was amplified by PCR with a set of primers (sodC-3 and sodC-4) using H44/76 chromosomal DNA as a template and cloned into pGEM-T vector (Promega) to construct pHT300. pHT300 was digested with PstI, then blunted and ligated to EcoRI linkers (Takara shuzo) to construct pHT303.…”

“…3). In this study, periplasmic Cu, Zn superoxide dismutase (SodC) [27,31,32] attached to a FLAG epitope (SodC-FLAG) (see Section 2) was used as a periplasmic protein marker. Almost equal amounts of proteins from each cellular fraction were analyzed by SDS-PAGE (Fig.…”

Bordetella pertussis fimbriae are effective carrier proteins in Neisseria meningitidis serogroup C conjugate vaccines

“…The mice were infected on day 35 using the intraperitoneal (i.p.) infection model [30]. Bacteria were grown in MHB broth for 4 h, adjusted to the required density with the same medium, and mixed with an equal volume of sterile human transferrin (40 mg ml 31 , Sigma) in PBS.…”