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
Author Information
Dukwon Lee: Research Institute of Agriculture and Life Sciences, Department of Agricultural Biotechnology, CALS, Seoul National University, Seoul 08826, Republic of Korea.
Hyojeong Lee: Research Institute of Agriculture and Life Sciences, Department of Agricultural Biotechnology, CALS, Seoul National University, Seoul 08826, Republic of Korea.
Kyumi Byun: School of Biological Sciences, Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, Republic of Korea.
Eun-Su Park: The Internship Program at the Food Biochemistry Laboratory, Department of Agricultural Biotechnology, CALS, Seoul National University, Seoul 08826, Republic of Korea.
Nam-Chul Ha: Research Institute of Agriculture and Life Sciences, Department of Agricultural Biotechnology, CALS, Seoul National University, Seoul 08826, Republic of Korea.
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.
