Cloning and sequence analysis of a rat liver cDNA encoding hydroxysteroid sulfotransferase.

Nothing has been known of the cDNAs encoding sulfotransferases (STs) that catalyze sulfation of steroids and xenobiotics. In the present study, a female Sprague-Dawley (SD) rat liver cDNA library was screened with rabbit anti-serum raised against hydroxysteroid ST a (STa) purified from female SD rat liver cytosol. The cDNA isolated from the library consisted of 1,028 base pairs which had an open reading frame of 852 base pairs encoding the entire rat ST subunit of 284 amino acids. The N-terminal amino acid sequences of STa and the rat liver hydroxysteroid ST, bile acid ST I, both elucidated previously by the chemical method, had a strong homology with that deduced from the cDNA. Northern blot analysis of total RNAs from female and male rat livers showed a marked sex difference (female much greater than male) in the expressed level of the mRNA for the predicted ST subunit protein. A remarkable sex difference (female much greater than male) was also observed by immuno-blot analysis in the level of the hydroxysteroid ST protein(s) cross-reacting with the anti-serum in the rat liver cytosols.