The cDNA cloning and transient expression of an ovary-specific 17 beta-hydroxysteroid dehydrogenase of chickens

A cDNA clone, pc17bHSD, was obtained from the chicken ovarian cDNA library by its partial homology to the cDNA sequence of the rat 17 beta-hydroxyster oid dehydrogenase (17 beta-HSD). The cDNA insert of pc17bHSD is 979 bp long and contains an open reading frame (ORF) of 906 bp. The deduced amino acid sequence of the ORF shows 48 and 50% overall identity with those of the ra t and the human type-1 17 beta-HSD, respectively. Five sequence regions com mon to the short-chain alcohol dehydrogenase superfamily are well conserved , including the YxxxK sequence motif at the active site. Northern blot hybr idization detected a transcript of about 1 kb only in ovaries of both sexua lly immature and mature female chickens. The 17 beta-HSD activity, which wa s highly specific to the interconversion between estrone and estradiol-17 b eta, was detected in the cytoplasmic fraction of human 293 cells transfecte d transiently with an expression vector carrying the c17bHSD cDNA sequence, pcDNAI/c17bHSD. From these results, it is concluded that the pc17bHSD is t he cDNA clone for the ovary-specific molecular species of 17 beta-HSD in ch ickens. (C) 1999 Elsevier Science B.V. All rights reserved.