Kinetics of hydrogen atom abstraction from substrate by an active site thiyl radical in ribonucleotide reductase.

ABSTRACT: Ribonucleotide reductases (RNRs) catalyze the conversion of nucleotides to deoxynucleotides in all organisms. Active E. coli class Ia RNR is an α2β2 complex that undergoes reversible, long-range proton-coupled electron transfer (PCET) over a pathway of redox active amino acids (β-Y122 → [β-W48] → β-Y356 → α-Y731 → α-Y730 → α-C439) that spans ∼35 Å. To unmask PCET kinetics from rate-limiting conformational changes, we prepared a photochemical RNR containing a [Re(I)] photooxidant site-specifically incorporated at position 355 ([Re]-β2), adjacent to PCET pathway residue Y356 in β. [Re]-β2 was further modified by replacing Y356 with 2,3,5-trifluorotyrosine to enable photochemical generation and spectroscopic observation of chemically competent tyrosyl radical(s). Using transient absorption sp

SUBMITTER: Olshansky L 

PROVIDER: S-EPMC4244835 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature