Duplicate genes for Fe-containing superoxide dismutase in Streptomyces coelicolor A3(2)

Streptomyces coelicolor Muller contains two types of superoxide dismutase ( SOD) containing Ni (encoded by sodN) or Fe (encoded by sodF). Unlike a sing le species of Fe-containing SOD in Muller strain, multiple forms of FeSODs were detected in S. coelicolor A3(2) strain by activity staining and Wester n blot analysis. Genomic Southern hybridization suggested the presence of a t least two copies of the sodF-like gene in A3(2). Two different genes for FeSOD (sodF1 and sodF2) were isolated from the phage library of A3(2) genom e. The nucleotide sequence of the sodF1 coding region was identical with th e unique sodF gene from Mailer while that of sodF2 shared 88% identity. The gene products of sodF1 and sonn were identified by activity staining and i mmunoblot analysis. Expression from the sodF1 gene was repressed by nickel as sensitively as Muller sodF, suggesting the presence of Ni-responsive reg ulatory site within the region shared by the two genes. Among 12 other Stre ptomyces species examined, only S. fradiae contained two FeSOD-like polypep tides. We postulate that the additional copy of the sodF gene (sodF2) was p rovided by the horizontal transfer from remotely related bacteria. (C) 1999 Elsevier Science B.V. All rights reserved.