Polymorphism of human Alpha class glutathione transferases

The recognition of the importance and utility of single nucleotide polymorphisms has generated an interest in the development of new strategies for their identification. Analysis of the Expressed Sequence Tag (EST) database can provide a rapid and efficient means of identifying polymorphisms. Screening of the Alpha class glutathione transferases (GSTs) in the EST database identified 10 putative polymorphisms in the coding region of the GSTA1 and GSTA2 genes, six of which were subsequently verified by sequence analysis. Polymerase chain reaction/restriction fragment length polymorphism analysis revealed the existence of three variants, a silent base substitution, K125K (G365A) in GSTA1, and T112S and E210A in GSTA2, in European Australian, African and Chinese populations. The variant isoforms of GSTA2 were expressed in Escherichia coli, purified, and enzymatically characterized. Modelling of the two GSTA2 polymorphisms into a three-dimensional structure of GSTA2, and characterization of their enzymatic properties, has shown that the structure and function of the wild-type GSTA2-2 isoenzyme is not significantly altered by these polymorphisms. This report demonstrates that analysis of the EST database provides a rapid and efficient means of identifying variant proteins.