Deciphering radical transport in the large subunit of class I ribonucleotide reductase.

ABSTRACT: Incorporation of 2,3,6-trifluorotyrosine (F(3)Y) and a rhenium bipyridine ([Re]) photooxidant into a peptide corresponding to the C-terminus of the ? protein (?C19) of Escherichia coli ribonucleotide reductase (RNR) allows for the temporal monitoring of radical transport into the ?2 subunit of RNR. Injection of the photogenerated F(3)Y radical from the [Re]-F(3)Y-?C19 peptide into the surface accessible Y731 of the ?2 subunit is only possible when the second Y730 is present. With the Y-Y established, radical transport occurs with a rate constant of 3 × 10(5) s(-1). Point mutations that disrupt the Y-Y dyad shut down radical transport. The ability to obviate radical transport by disrupting the hydrogen bonding network of the amino acids composing the colinear proton-coupled electron transfer pathway in ?2 suggests a finely tuned evolutionary adaptation of RNR to control the transport of radicals in this enzyme.

SUBMITTER: Holder PG 

PROVIDER: S-EPMC3268775 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature