Corynebacterium glutamicum sdhA encoding succinate dehydrogenase subunit A plays a role in cysR-mediated sulfur metabolism.

The Corynebacterium glutamicum CysR protein plays a critical regulatory role in sulfur metabolism. In this study, we isolated a protein interacting with CysR by employing a two-hybrid system. Subsequent analysis identified the gene as sdhA annotated to encode succinate dehydrogenase flavoprotein subunit A, a Krebs cycle enzyme. Deletion of the gene (ΔsdhA) severely affected cell growth and final cell yield, particularly in complex media. In addition, the ΔsdhA mutant strain was unable to use acetate as the sole carbon source, showing the identity of the gene. Transcription of the cysR gene and genes known to be regulated by cysR was affected in the ΔsdhA mutant strain, suggesting a positive role for sdhA on cysR. Furthermore, ΔsdhA cells showed increased sensitivity to oxidants, such as diamide, menadione, and hydrogen peroxide. In ΔsdhA cells, the trx gene, which encodes thioredoxin reductase, was severely repressed. Taken together, our findings show that the SdhA protein not only performs a role as a TCA enzyme but also communicates with sulfur metabolism, thereby regulating genes involved in redox homeostasis.