Characterization of macaque 3β-hydroxy-5-ene steroid dehydrogenase/Δ 5-Δ 4 isomerase: structure and expression in steroidogenic and peripheral tissues in primate

Abstract

The conversion of 3β-hydroxy-5-ene steroids by the enzyme complex 3β-hydroxysteroid dehydrogenase/Δ 5-Δ 4 isomerase (3β-HSD) is an obligatory step in the biosynthesis of all classes of hormonal steroids in classical steroidogenic as well as in peripheral tissues. To develop a model more closely related to the human, we have isolated and characterized cDNA clones encoding macaque 3β-HSD by screening a rhesus monkey ovary κgt11 cDNA library using a human 3β-HSD cDNA probe. Nucleotide sequence of 1629 bp from overlapping cDNA clones predicts a protein of 372 amino acids with a calculated molecular mass of 41,874 (excluding the first Met). The deduced amino acid sequence of macaque 3β-HSD displays 79.4% and 93.9% similarity with that of bovine and human 3β-HSD, respectively. RNA blot analysis performed under high stringency conditions of macaque poly(A) + RNA samples using full-length 32P-labeled macaque 3β-HSD cDNA revealed the presence of an approximately 1.7 kb mRNA species in classical steroidogenic tissues, namely the ovary, testis and adrenal glands as well as in several peripheral tissues including the liver, kidney and epididymis. Computer analysis of the deduced macaque 3/gb-HSD protein sequence predicts the presence of an NH 2-terminal membrane-associated segment as well as four additional membrane-spanning segments, thus suggesting that 3β-HSD is an integral protein. The availability of macaque cDNA should permit detailed studies concerning the tissue-specific expression as well as the hormonal regulation of 3β-HSD mRNA in classical steroidogenic glands as well as in peripheral tissues which are an important site of Steroidogenesis in primates.