TheSCO2299gene fromStreptomyces coelicolorA3(2) encodes a bifunctional enzyme consisting of an RNase H domain and an acid phosphatase domain.

TheSCO2299gene fromStreptomyces coelicolorencodes a single peptide consisting of 497 amino acid residues. Its N-terminal region shows high amino acid sequence similarity to RNase HI, whereas its C-terminal region bears similarity to the CobC protein, which is involved in the synthesis of cobalamin. TheSCO2299gene suppressed a temperature-sensitive growth defect of anEscherichia coliRNase H-deficient strain, and the recombinant SCO2299 protein cleaved an RNA strand of RNA·DNA hybridin vitro. The N-terminal domain of the SCO2299 protein, when overproduced independently, exhibited RNase H activity at a similar level to the full length protein. On the other hand, the C-terminal domain showed no CobC-like activity but an acid phosphatase activity. The full length protein also exhibited acid phosphatase activity at almost the same level as the C-terminal domain alone. These results indicate that RNase H and acid phosphatase activities of the full length SCO2299 protein depend on its N-terminal and C-terminal domains, respectively. The physiological functions of theSCO2299gene and the relation between RNase H and acid phosphatase remain to be determined. However, the bifunctional enzyme examined here is a novel style in the Type 1 RNase H family. Additionally,S. coelicoloris the first example of an organism whose genome contains three active RNase H genes. [ABSTRACT FROM AUTHOR]