Class II Ribonucleotide Reductases Catalyze Carbon−Cobalt Bond Reformation on Every Turnover
| Autor: | Christopher C. Lawrence, Stuart Licht, JoAnne Stubbe |
|---|---|
| Rok vydání: | 1999 |
| Předmět: |
chemistry.chemical_classification
Conformational change Ribonucleotide biology Stereochemistry Chemistry Allosteric regulation Active site General Chemistry Biochemistry Catalysis Adenosylcobalamin Cofactor Homolysis Colloid and Surface Chemistry biology.protein medicine heterocyclic compounds Nucleotide medicine.drug |
| Zdroj: | Journal of the American Chemical Society. 121:7463-7468 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja9913840 |
| Popis: | Ribonucleoside triphosphate reductase (RTPR) from Lactobacillus leichmannii catalyzes the reduction of nucleotides to deoxynucleotides with concomitant oxidation of two cysteines within the active site to a disulfide. RTPR requires adenosylcobalamin (AdoCbl) as a cofactor and as a radical chain initiator. Catalysis is initiated by homolysis of the carbon−cobalt bond of AdoCbl to yield cob(II)alamin, 5‘-deoxyadenosine, and a protein-based thiyl radical. The turnover numbers for ATP with its allosteric effector dGTP, and for CTP with its allosteric effector dATP, are both 2 s-1. The rate-limiting step for turnover in the steady state is re-reduction of the oxidized form of the protein, a conformational change, or both. Under conditions where [RTPR] ≫ [AdoCbl], the rates of ATP and CTP reduction do not vary linearly with [AdoCbl] but instead exhibit saturation behavior with turnover numbers of 10 s-1 (ATP) and 8.5 s-1 (CTP). This result suggests that dissociation of AdoCbl, which requires carbon−cobalt bond ... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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