A cDNA clone, pcSCC1, isolated from a chicken adrenal gland library showed about 62% nucleotide sequence similarity to those of mammalian and rainbow trout P-450scc cDNAs and was proved to be the clone for chicken P-450scc by the enzymatic activity of converting 25-hydroxycholesterol to pregnenolone demonstrated in the transfected COS-7 cells. Comparison of deduced amino acid sequences shows significant conservation of heme- and steroid-binding domains but little similarity in the putative N-terminal presequence region among chicken, trout and mammals. The chicken cDNA lacks a polyadenylation signal in its 3'-UTR. Sequencing of a 3' end region of the P-450scc gene (CYP11A1) suggests that a region containing the polyadenylation signal is spliced out from the pre-mRNA.
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