Photochemical Rescue of a Conformationally Inactivated Ribonucleotide Reductase.
J Am Chem Soc
; 140(46): 15744-15752, 2018 11 21.
Article
em En
| MEDLINE
| ID: mdl-30347141
ABSTRACT
Class Ia ribonucleotide reductase (RNR) of Escherichia coli contains an unusually stable tyrosyl radical cofactor in the ß2 subunit (Y122â¢) 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 α2ß2 complex from the Y122⢠site in ß2 to the substrate activating cysteine residue (C439) in α2 via a pathway of redox active amino acids (Y122[ß] â W48[ß]? â Y356[ß] â Y731[α] â Y730[α] â C439[α]) spanning >35 Å. Ionizable residues at the α2ß2 interface are essential in mediating RT, and therefore control activity. One of these mutations, E350X (where X = A, D, Q) in ß2, obviates all RT, though the mechanism of control by which E350 mediates RT remains unclear. Herein, we utilize an E350Q-photoß2 construct to photochemically rescue RNR activity from an otherwise inactive construct, wherein the initial RT event (Y122⢠â Y356) is replaced by direct photochemical radical generation of Y356â¢. These data present compelling evidence that E350 conveys allosteric information between the α2 and ß2 subunits facilitating conformational gating of RT that specifically targets Y122⢠reduction, while the fidelity of the remainder of the RT pathway is retained.
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Base de dados:
MEDLINE
Assunto principal:
Ribonucleotídeo Redutases
Idioma:
En
Ano de publicação:
2018
Tipo de documento:
Article