Characterization of moeB--part of the molybdenum cofactor biosynthesis gene cluster in Staphylococcus carnosus

Transposon mutagenesis of Staphylococcus carnosus led to the identification of a gene cluster comprising nine genes that are important for molybdenum cofactor biosynthesis. Two nitrate-reductase-negative Tn917-insertion mutants were defective in MoeB. In cell-free extracts of an moeB mutant, the molybdenum-cofactor-deficient nitrate reductase could be reconstituted with a low-molecular-mass component (most likely free molybdenum cofactor) from an S. carnosus mutant that is defective in the nitrate reductase structural genes. The expression of moeB was studied in response to oxygen and nitrate. Primer-extension studies indicated that anaerobiosis and nitrate each enhance transcription of moeB.