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AZaserine Affinity Labelling of 
-Glutamyl Transferase of Hydra Attenuata Without Inactivation of the Glutathione Receptor
1 Department of Cell and Developmental Biology, University of California Irvine, California 92717
2 Department of Molecular Pharmacology, Albert Einstein College of Medicine Bronx, NY 10461
3 Departments of Biological Chemistry and Physiology and Biophysics, Washington University School of Medicine St. Louis, Missouri 63110
Intrigued by similar specificities of the hydra feeding receptor and 
-glutamyl transferase activity toward GSH, we examined the possibility that these two GSH-bihding activities might reside in the same protein. We find that the two activities differ in specificity toward the -glutamyl moiety of GSH. The hydra transferase recognizes L-azaserine, L-Glu, D-Glu and L-Gln. The feeding receptor recognizes only L-GlU and L-Gln; L-azaserine and D-Glu have no effect. L-azaserine, known to bind covalently to the -glutamyl donor site of mammalian transferase, irreversibly inactivates hydra transferase activity. The transferase affinity label, however, has no effect on the GSH-stimulated feeding response, permitting us to demonstrate that these two activities have different GSH recognition sites and appear to reside in different proteins.
Note:
Present address and for correspondence: Department of Microbiology, University of Massachusetts, Amherst, Ma. 01002.
Present address: National Institute for Occupational Safety and Health, Biochemistry Section, 944 Chestnut Ridge Road, Morgantown, W. Va. 26505.
Submitted on April 19, 1982
