A lysR‐type regulator is involved in the negative regulation of genes encoding selenium‐free hydrogenases in the archaeon Methanococcus voltae

Summary The archaeon Methanococcus voltae encodes two pairs of NiFe‐hydrogenase isoenzymes. One hydrogenase of each pair contains selenium in the active site, whereas the other one is selenium‐free. The gene groups for the selenium‐free hydrogenases, called vhc and frc, are linked by a common intergenic region. They are only transcribed under selenium limitation. A protein binding to a negative regulatory element involved in the regulation of the two operons was purified by DNA‐affinity chromatography. Through the identification of the corresponding gene the protein was found to be a LysR‐type regulator. It was named HrsM (hydrogenase gene regulator, selenium dependent in M. voltae). hrsM knockout mutants constitutively transcribed the vhc and frc operons in the presence of selenium. A putative HrsM binding site was also detected in the intergenic region in front of the hrsM gene. Northern blot analysis indicated that the hrsM gene might be autoregulated.