Molecular cloning and expression of a guinea pig 3-hydroxysteroid sulfotransferase distinct from chiral-specific 3 alpha-hydroxysteroid sulfotransferase.

A guinea pig adrenal hydroxysteroid sulfotransferase (gpHST2) has been cloned that is distinct from guinea pig hydroxysteroid sulfotransferase that stereoselectively acts on 3 alpha-hydroxylated neutral steroids (gp3 alpha HST, redesignated gpHST1). The deduced amino acid sequences for gpHST1 and gpHST2 are 86% identical; however, whereas gpHST1 selectively acts on 3 alpha-hydroxylated steroids, gpHST2 demonstrates a clear preference (but not exclusive specificity) for 3 beta-hydroxylated steroids suggesting that gpHST2 is similar to a previously reported guinea pig hydroxysteroid sulfotransferase that selectively acts on 3 beta-hydroxylated neutral steroids (gp3 beta HST). Additionally, gpHST2 (33K) is the same size as gp3 beta HST and larger than gpHST1 (32K), contains amino acid sequences identical to peptides obtained from gp3 beta HST and cross-reacts with antibodies raised against purified gp3 beta HST. Nonetheless, gpHST2 can sulfonate both 3 alpha- and 3 beta-hydroxylated neutral steroids, suggesting that either gp3 beta HST does not have the exquisite stereoselectivity previously indicated or this subfamily of hydroxysteroid sulfotransferases is larger than originally thought.