Molecular cloning of dimethyl sulfoxide reductase from Rhodobacter sphaeroides

The dsrA gene encoding the molybdoenzyme dimethyl sulfoxide reductase was isolated by screening phagemid libraries containing restriction fragments of Rhodobacter sphaeroides f. sp. denitrificans genomic DNA with a pool of degenerate oligonucleotides. The encoded 822 amino-acid protein includes a 42 amino-acid periplasmic signal sequence that is cleaved during activation of the enzyme. Both forms of the protein were heterologously expressed in inactive states in E. coli and identified by Western blot analysis.