Photochemical Rescue of a Conformationally Inactivated Ribonucleotide Reductase
| Autor: | Daniel G. Nocera, Brandon L. Greene, JoAnne Stubbe |
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| Rok vydání: | 2018 |
| Předmět: |
Models
Molecular 0301 basic medicine Conformational change Free Radicals Protein Conformation Stereochemistry Allosteric regulation 010402 general chemistry 01 natural sciences Biochemistry Article Catalysis Cofactor Electron Transport 03 medical and health sciences Colloid and Surface Chemistry Ribonucleotide Reductases Escherichia coli Nucleotide chemistry.chemical_classification biology Effector General Chemistry Photochemical Processes 0104 chemical sciences Amino acid 030104 developmental biology Ribonucleotide reductase chemistry biology.protein Cysteine |
| Zdroj: | Journal of the American Chemical Society. 140:15744-15752 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | Class Ia ribonucleotide reductase (RNR) of Escherichia coli contains an unusually stable tyrosyl radical cofactor in the β2 subunit (Y122•) necessary for nucleotide reductase activity. Upon binding the cognate α2 subunit, loaded with nucleoside diphosphate substrate and an allosteric/activity effector, a rate determining conformational change(s) enables rapid radical transfer (RT) within the active α2β2 complex from the Y122• site in β2 to the substrate activating cysteine residue (C439) in a2 via a pathway of redox active amino acids (Y122[β] ↔ W48[β]? ↔ Y356[β] ↔ Y731[α] ↔ Y730[α] ↔ C439[α]) spanning >35 Å. Ionizable residues at the α2β2 interface are essential in mediating RT, and therefore control activity. One of these mutations, E350X (where X = A, D, Q) in β2, obviates all RT, though the mechanism of control by which E350 mediates RT remains unclear. Herein, we utilize an E350Q-photoβ2 construct to photochemically rescue RNR activity from an otherwise inactive construct, wherein the initial RT event (Y122• → Y356) is replaced by direct photochemical radical generation of Y356•. These data present compelling evidence that E350 conveys allosteric information between the a2 and β2 subunits facilitating conformational gating of RT that specifically targets Y122• reduction, while the fidelity of the remainder of the RT pathway is retained. |
| Databáze: | OpenAIRE |
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