The human liver glutathione s-transferase gene superfamily: Expression and chromosome mapping of an H_b subunit cDNA

We have isolated from a λgtl0 cDNA library a clone λGTH4 which encodes a human liver glutathione S-transferase H_b subunit, designated as subunit 4. Expression of this cDNA in E. coli and subsequent purification and immunoblotting analysis provided a definitive assignment of a structure and function relationship. RNA blot hybridization with human liver poly(A) RNA revealed a single band of ∼1200 nucleotides, comparable in size to the rat brain Y_b3 mRNA. Divergence analysis of amino acid replacement sites in subunit 4 relative to the four rat Y_b subunits revealed that it is most closely related to the brain-specific Y_b3 subunit. This conclusion is further substantiated by the nucleotide sequence homology between λGTH4 and the Y_b3 cDNA in their 3′ untranslated region. In situ chromosome mapping has located this glutathione S-transferase gene in the region of p31 on chromosome 1. Results from many laboratories, including ours, indicate that the human glutathione S-transferases are encoded by a gene superfamily which is located on at least two different chromosomes.