title: Differential sensitivities of the subunits of mammalian ribonucleotide reductase to proteases, sulfhydryl reagents, and heat.
abstract: Ribonucleotide reductase catalyzes the rate-limiting step in the formation of 2'-deoxyribonucleoside 5'-triphosphates. It consists of two nonidentical protein subunits, the nonheme iron subunit, and the effector-binding subunit. It has previously been shown that these two components making up the active enzyme species are not coordinately synthesized or degraded. It was found that the effector-binding subunit was more sensitive to proteolysis by chymotrypsin, to heating at 55 degrees C, and to the sulfhydryl reagents, pCMB and NEM. The nonheme iron subunit was more sensitive to trypsin treatment. ATP and dATP protected the effector-binding subunit from proteolytic inactivation. Neither ATP nor CDP protected the effector-binding subunit from inactivation by the sulfhydryl reagents. These data indicate that the protein properties of the two subunits of mammalian ribonucleotide reductase are significantly different.
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000201:enzymology; D002918:Chymotrypsin / Q000494:pharmacology; D006358:Hot Temperature; D051379:Mice; D008813:Mice, Inbred ICR; D010447:Peptide Hydrolases / Q000494:pharmacology*; D012264:Ribonucleotide Reductases / Q000032:analysis*; D013439:Sulfhydryl Reagents / Q000494:pharmacology*; D014357:Trypsin / Q000494:pharmacology
chemical_list: D013439:Sulfhydryl Reagents; D000255:Adenosine Triphosphate; D012264:Ribonucleotide Reductases; D010447:Peptide Hydrolases; D002918:Chymotrypsin; D014357:Trypsin