Structural analysis of a rat liver glutathione S-transferase Ya gene.

We have isolated and characterized a complete structural gene encoding a rat liver glutathione S-transferase (glutathione transferase; EC 2.5.1.18) Ya subunit. The gene spans approximately 11 kilobases and is comprised of seven exons separated by six introns. A sequence similar to the Goldberg-Hogness promoter ("TATA" box), TATTA, is located 32 base pairs upstream from the transcription initiation site. Exons 2 and 4 of the glutathione S-transferase gene encode amino acid sequences of the Ya subunit that are highly conserved in the Yc subunit, whereas exons 3 and 5 encode amino acids that are divergent in the Yc subunit. These data suggest that exons 2 and 4 may encode domains of the Ya subunits that have similar structural or functional properties to the corresponding domains in the Yc subunit (e.g., glutathione binding site), whereas exons 3 and 5 may encode domains of the Ya subunit that have unique structural or functional properties to the corresponding domains in the Yc subunit (e.g., substrate binding site).