Structural and functional analysis of the TetR-family transcriptional regulator SCO0332 from Streptomyces coelicolor

SCO0332 protein is a putative TetR-family transcriptional regulator from Streptomyces coelicolor A3(2). The crystal structure of SCO0332 was determined at 2.25 Å resolution by single-wavelength anomalous diffraction (SAD) phasing using the S atoms of the native protein. SCO0332 contains a helix-turn-helix (HTH) DNA-binding motif in its N-terminal region and forms a homodimer. The overall structure of SCO0332 shows significant similarity to other TetR-family regulators. A systematic evolution of ligands by exponential enrichment (SELEX) analysis indicated that SCO0332 has sequence-specific DNA-binding ability and determined the position of the operator element of SCO0332 on the chromosomal DNA of S. coelicolor. An electrophoretic mobility-shift assay (EMSA) showed that SCO0332 binds to the operator sequence upstream of the sco0330 gene, which encodes a putative short-chain oxidoreductase. These results suggest that SCO0332 is a transcriptional repressor that regulates sco0330 gene expression.