Characterization of a cDNA for human glutathione-insulin transhydrogenase (protein-disulfide isomerase/oxidoreductase).
A human liver cDNA expression library in lambda-phage gt11 was screened with monoclonal antibodies to rat liver protein-disulfide isomerase/oxidoreductase (EC 5.3.4.1/1.8.4.2), also known as glutathione-insulin transhydrogenase (GIT). The nucleotide sequence of the largest cDNA insert (hgit-1) was determined. It contained approx. 1500 basepairs, representing an estimated 65% of the glutathione-insulin transhydrogenase message. The amino-acid sequence deduced from this cDNA insert contains a 7-amino-acid long polypeptide determined by sequencing the active-site fragment isolated from the rat GIT protein. A comparison of the nucleotide sequence of hgit-1 and a previously reported nucleotide sequence of rat glutathione-insulin transhydrogenase cDNA shows that the human hgit-1 clone corresponds to the middle of the transhydrogenase message at amino-acid residue number 275 of the rat protein, and codes for 206 amino-acid residues, including one of the two active-site regions of glutathione-insulin transhydrogenase, a stop codon (TAA), a long 3'-noncoding region of over 800 bases, a polyadenylation signal (AATAA), and a 29 base poly(A) tail. There exists high homology between the human and rat enzymes (94% in the overall amino-acid sequence, with 100% in the active site region and 81% in the nucleotide sequence within the coding portion of hgit-1). As with the rat enzyme, the human enzyme shows some identity with another dithiol-disulfide-exchange protein, Escherichia coli thioredoxin. Like rat cDNA, the human hgit-1 cDNA hybridized to rat mRNA of 2500 bases on a Northern blot. The relative quantitative abundance of GIT mRNA in nine rat tissues studied using hgit-1 as a hybridization probe was found to be in the same order as previously found with the rat cDNA. Thus, the above studies indicate that glutathione-insulin transhydrogenase is a highly conserved protein and that the human hgit-1 cDNA is suitable for use as a probe for further studies on gene regulation of this enzyme.
Morris
J I
JI
Division of Endocrinology, School of Medicine, Wright State University, Dayton, OH 45435.
Varandani
P T
PT
D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D006801:Humans; D007535:Isomerases / Q000235:genetics*; D008969:Molecular Sequence Data; D010088:Oxidoreductases / Q000235:genetics*; D011490:Protein Disulfide Reductase (Glutathione) / Q000235:genetics*; D019704:Protein Disulfide-Isomerases
D004247:DNA; D010088:Oxidoreductases; D011490:Protein Disulfide Reductase (Glutathione); D007535:Isomerases; D019704:Protein Disulfide-Isomerases