Molecular cloning and characterization of mouse glutatmonesynthetase gene

We have isolated and characterized the cDNA and genomic clones encoding mouse glutathione synthetase (GSH syn), the enzyme that catalyzes the last step in the synthesis of glutathione. A full length mouse cDNA, obtained from a kidney cDNA library screened with Xenapus cDNA probes, shows a 95% sequence identity to a recently cloned rat cDNA, and predicts an open reading frame (ORF) of 474 aa. Steady state RNA levels corresponding to the cDNA are the highest in kidney and about three fold lower in liver and are in good agreement with GSH syn enzyme levels in tissues. The gene is a single copy gene spanning -30 kb and consists of at least 15 exons. As a result of alternative transcription initiation and alternative splicing among the first 5 exons, this gene encodes 6 different GSH Syn RNAs: AI, A2, A3, B, Cl and C2. Type A RNAs are different at their 5'ends but have the same 474 aa ORF. Types B and C RNAs all have unique 5'ends, but appear to share two different ORFs that are both shorter than that for types A1-A3 and contain unique amino termini. RNase protection analysis reveals that in mouse kidney 90% of GSH syn RNA is type A (mostly Al), another 10% can be accounted for by types B, Cl and C2; while in liver, almost all the GSH syn RNA is type Al. We have demonstrated the biological activity of type Al cDNA in a complement transformation assay in yeast strains deficient in GSH syn. (This work was supported by N1H Grants CA-39392 (MWL) and GM 49119 (SS)).