Comparative Proteomic Analysis of Hydrogen Peroxide-Induced Protein Expression in Streptococcus pneumoniae D39

초록

Background: Streptococcus pneumoniaeis a leading cause of human respiratory tract in-fection. Despite the lack of activities of antioxidative enzymes, including cytochromes, hemopro-teins, and peroxidases/catalases, traits conferring the aerotolerant-anaerobic growth of this bacteri-um are conserved, with the high efficacy of antioxidative actions, in an oxygen-rich environment. Objective: Through proteome analysis, this study's intention was to evaluate differentially ex-pressed proteins and/or gene products modeled in a highly virulent strain, S. pneumoniae D39, ex-ogenously-treated with millimolar concentrations of H2O2. Methods: For two-dimensional gel electrophoresis (2-DE) analysis, following one dimensional iso-electric focusing with an immobilized pH gradient of pH 4-7, the most significantly mobilized pro-teins expressed were separated by SDS-PAGE in the second dimension. With a total of 431 protein spots detected, certain proteins were excised, in-gel trypsin digested, and analyzed by combination with MALDI-TOF and LC-ESI-MS/MS for mass spectrometric peptide mapping and protein identi-fication. Utilizing mass spectrometry analysis of spots excised from 2-DE, the selected protein spots were identified with a variety of databases and MASCOT. Results: With the aid of comparisons to proteome reference maps, the most differentially ex-pressed 38 proteins, those with approximately 1.4-fold or more increase and/or decrease or with multiple isoforms exhibiting variable pIvalues, were induced by treatment of exogenous 2 mM H2O2.The identified proteins were seen to be involved in pneumococcal pathogenesis and primary metabolism, amongst others. Conclusion: This is the first study to convincingly document proteomic information associated with pathophysiological adaptation under the given oxidative conditions, and corresponding poten-tial antioxidative mechanisms, in S. pneumoniae.

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