Abstract
The cholesterol oxidase gene (choA) of Streptomyces sp. was cloned into S. lividans. The cloned cells of S. lividans produced several fold more cholesterol oxidase extracellularly than did the original producing strain. We determined the entire nucleotide sequence of the choA gene and found an open reading frame encodes a mature cholesterol oxidase of 504 amino acids with a Mr of 54,913. The signal sequence extends over 42 amino acids. Regions of homology with flavoproteins were identified in the cholesterol oxidase. The promoter for choA exists about 1.3 kb upstream from choA. Thus, we sequenced the fragment between the promoter and the choA gene and we found another open reading frame (381 amino acids, Mr 41668) which has a high degree of homology to the Pseudomonas P-450 CAM and conserves the HR2 region in cytochrome P-450s. The mRNA start sites and sizes of their transcripts were determined. Here, we proposed a new operon model concerned with a sterol metabolism in Streptomyces.
