Journal of Microbiology

Research Article

Functional importance of Ser323 in cysteine desulfhydrase and cystathionine gamma-lyase MccB of Staphylococcus aureus: Dukwon Lee, Hyojeong Lee, Kyumi Byun, Eun-Su Park, Nam-Chul Ha; J. Microbiol. 2025;63(2):e2411026. Published online February 27, 2025; DOI: https://doi.org/10.71150/jm.2411026

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Abstract PDF Supplementary Material: Pyridoxal 5'-phosphate (PLP)-dependent enzymes participate in various reactions involved in methionine and cysteine metabolism. The representative foodborne pathogen Staphylococcus aureus expresses the PLP-dependent enzyme MccB, which exhibits both cystathionine gamma-lyase (CGL) and cysteine desulfhydrase activities. In this study, we investigated the role of Ser323 in MccB, a conserved residue in many PLP-dependent enzymes in the transsulfuration pathway. Our findings reveal that Ser323 forms a hydrogen bond with the catalytic lysine in the absence of PLP, and upon internal aldimine formation, PLP-bound lysine is repositioned away from Ser323. Substituting Ser323 with alanine abolishes the enzymatic activity, similar to mutations at the catalytic lysine site. Spectroscopic analysis suggests that Ser323 is essential for the rapid formation of the internal aldimine with lysine in wild-type MccB. This study highlights the crucial role of Ser323 in catalysis, with broader implications for other PLP-dependent enzymes, and enhances our understanding of the molecular mechanisms involved in the selective control of foodborne pathogenic bacteria.

Journal Article

Structural and Functional Analyses of the Flavoprotein Disulfide Reductase FN0820 of Fusobacterium nucleatum: Hyunwoo Shin , Yeongjin Baek , Dukwon Lee , Yongbin Xu , Yonghoon Kwon , Inseong Jo , Nam-Chul Ha; J. Microbiol. 2023;61(12):1033-1041. Published online December 20, 2023; DOI: https://doi.org/10.1007/s12275-023-00095-9

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Escherichia coli RclA and Staphylococcus aureus MerA are part of the Group I flavoprotein disulfide reductase (FDR) family and have been implicated in the contribution to bacterial pathogenesis by defending against the host immune response. Fusobacterium nucleatum is a pathogenic, anaerobic Gram-negative bacterial species commonly found in the human oral cavity and gastrointestinal tract. In this study, we discovered that the F. nucleatum protein FN0820, belonging to the Group I FDR family, exhibited a higher activity of a Cu2+- dependent NADH oxidase than E. coli RclA. Moreover, FN0820 decreased the dissolved oxygen level in the solution with higher NADH oxidase activity. We found that L-tryptophan and its analog 5-hydroxytryptophan inhibit the FN0820 activities of NADH oxidase and the concomitant reduction of oxygen. Our results have implications for developing new treatment strategies against pathogens that defend the host immune response with Group I FDRs.

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The role of metals in hypothiocyanite resistance in Escherichia coli
Michael J. Gray, Laurie E. Comstock
Journal of Bacteriology.2024;[Epub] CrossRef

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