Alteration in structure of multifunctional protein from Chinese hamster ovary cells defective in pyrimidine biosynthesis*
AUTOR(ES)
Davidson, Jeffrey N.
RESUMO
A combined genetic, biochemical, and immunological approach has clarified structural relationships involving the first three 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-orotase (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 molecular weight from those of CHO-K1. The results presented permit the conclusion that (i) these three enzymes reside in a single multifunctional 220,000-dalton polypeptide; (ii) the aspartate transcarbamoyltransferase activity is located on a portion (≈20,000 daltons) at one end of the polypeptide; (iii) this portion may also be required for monomers to aggregate into the multimeric from present in mammalian cells; (iv) the mutations in Urd-A and the Urd-A revertants lie in the structural gene for this multifunctional protein; and (v) increased sensitivity to proteases could account for the alterations in the structure of these enzymes in the mutants.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=383464Documentos Relacionados
- Oligomeric structure of the multifunctional protein CAD that initiates pyrimidine biosynthesis in mammalian cells.
- Structure of the dihydrofolate reductase gene in Chinese hamster ovary cells.
- Defective regulation of cholesterol biosynthesis and plasma membrane fluidity in a Chinese hamster ovary cell mutant.
- Demethylation enhances removal of pyrimidine dimers from the overall genome and from specific DNA sequences in Chinese hamster ovary cells.
- Defective transport of Sindbis virus glycoproteins in End4 mutant Chinese hamster ovary cells.