Oxidation-reduction reactions are critical mechanisms which regulate many enzymatic reactions in the cell, both during growth and quiescence. The reduction of ribonucleotides to the corresponding deoxyribonucleotides, needed for DNA synthesis during cell proliferation, is catalyzed by the enzyme ribonucleotide diphosphate reductase. Glutaredoxin is a glutathione (GSH)-dependent hydrogen donor for ribonucleotide diphosphate reductase and contains the active peptide site encoded by the amino acid residue sequence -C-P-Y-C- (SEQ ID NO:6). This consensus sequence is conserved in glutaredoxin from such different organisms as E. coli, vaccinia virus, yeast, plants, and mammalian cells. Glutaredoxin has inherent GSH-disulphide oxidoreductase (thioltransferase) activity in a coupled system with GSH, NADPH, and GSH-reductase, catalyzing the reduction of low molecular weight disulphides as well as proteins. Glutaredoxin has been proposed to exert a general thiol redox control of protein activity by acting both as an effective protein disulphide reductase, similar to thioredoxin, and as a specific GSH-mixed disulphide reductase (Padilla, Calif. et al. (1996) FEBS Lett. 378:69-73).
In addition to their important role in DNA synthesis and cell division, glutaredoxin and other thioproteins provide effective antioxidant defense against oxygen radicals and hydrogen peroxide (Schallreuter, K. U. and Wood, J. M. (1991) Melanoma Res. 1:159-167). Glutaredoxin is the principal agent responsible for protein dethiolation in vivo and reduces dehydroascorbic acid in normal human neutrophils (Jung, C. H. and Thomas, J. A. (1996) Arch. Biochem. Biophys. 335:61-72; Park, J. B. and Levine, M. (1996) Biochem. J. 315:931-938).
The human glutaredoxin cDNA encodes an approximately 12 kDa protein. Site-directed mutagenic studies suggest that replacement of C-7 with S-7 reduced the tendency of the protein to form homodimers and that the N-terminal M-1 is removed during cellular processing (Padilla, Calif. et al. (supra)). Three heat-labile proteins which have glutaredoxin-like properties have been isolated from HeLa cells. Two have a molecular mass of approximately 12 kDa, and the other has a molecular mass of greater than 30 kDa (Tsang, M. L. and Weatherbee, J. A. (1981) Proc. Natl. Acad. Sci. 78:7478-7482). Glutaredoxin has also been identified in plant tissues and in yeast (GenBank accession number Z49699; Gan, Z. R. (1992) Biochem. Biophys. Res. Comm. 187:949-955).
Nitrosourea anti-tumor drugs covalently deactivate ribonucleotide reductase by alkylating the thiolate active site. Deactivation prevents further thioltransferase activity by glutaredoxin and could determine the cytostatic properties of these drugs (Schallreuter, K. U. et al. (1990) Biochim. Biophys. Acta 1054:14-20).
The discovery of a new human glutaredoxin .beta. and the polynucleotides encoding it satisfies a need in the art by providing new compositions which are useful in the diagnosis, prevention, and treatment of immunological and neoplastic disorders.