PRIMARY STRUCTURE AND PROPERTIES OF GLUTATHIONE-REDUCTASE FROM ARABIDOPSIS-THALIANA

A cDNA encoding glutathione reductase (EC 1.6.4.2) from Arabidopsis thaliana was cloned by immunoscreening. The amino acid sequence deduced from the nucleotide sequence agrees with the N-terminal amino acid sequence of the major isozyme (GR II) purified from leaves of A. thaliana. The predicted polypeptide comprises an N-terminal leader sequence of 74 amino acids, which has features of chloroplast-targeting peptides, and a mature polypeptide of 491 residues with a molecular mass of 52.7 kDa, which shows homology with glutathione reductases from other species. The K(m) for GSSG was 44 muM and that for NADPH was 5.0 muM for GR II at 25-degrees-C. The pH optimum for GR II was 7.5 to 8.0. The native molecular mass of GR II was 110 kDa, indicating that GR II is a homodimer. GR II had an isoelectric point of 4.8. The cDNA hybridizes with a 2.1-kb poly(A)+RNA from leaves of A. thaliana. Genomic Southern analysis indicates that the gene corresponding to the cDNA is likely a single-copy gene.