Alteration in structure of multifunctional protein from Chinese hamster ovary cells defective in pyrimidine biosynthesis
- 1 April 1979
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 76 (4) , 1731-1735
- https://doi.org/10.1073/pnas.76.4.1731
Abstract
A combined genetic, biochemical, and immunological approach has clarified structural relationships involving the 1st 3 enzymes of de novo pyrimidine biosynthesis. A procedure involving antibody and protein A-Sepharose was used to isolate the enzymes carbamoyl-phosphate synthase [ATP:carbamate phosphotransferase (dephosphorylating, amido-transferring), EC 2.7.2.9], aspartate transcarbamoyltransferase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2), and dihydro-ortase (L-5,6-dihydroorotate amidohydrolase, EC 3.5.2.3) from Chinese hamster ovary cell CHO-K1, the uridine-requiring auxotroph Urd-A, and selected Urd-A revertants. The enzymes of Urd-A and the Urd-A revertants were significantly altered in activity, native structure, and MW from those of CHO-K1. These 3 enzymes apparently reside in a single multifunctional 220,000-dalton polypeptide; the aspartate transcarbamoyltransferase activity is located on a portion (.apprxeq. 20,000 daltons) at one end of the polypeptide; this portion may also be required for monomers to aggregate into the multimeric form present in mammalian cells; the mutations in Urd-A and the Urd-A revertants lie in the structural gene for this multifunctional protein; and increased sensitivity to proteases could account for the alterations in the structure of these enzymes in the mutants.This publication has 15 references indexed in Scilit:
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