A tyrosine-tryptophan dyad and radical-based charge transfer in a ribonucleotide reductase-inspired maquette.

ABSTRACT: In class 1a ribonucleotide reductase (RNR), a substrate-based radical is generated in the ?2 subunit by long-distance electron transfer involving an essential tyrosyl radical (Y122O·) in the ?2 subunit. The conserved W48 ?2 is ?10?Å from Y122OH; mutations at W48 inactivate RNR. Here, we design a beta hairpin peptide, which contains such an interacting tyrosine-tryptophan dyad. The NMR structure of the peptide establishes that there is no direct hydrogen bond between the phenol and the indole rings. However, electronic coupling between the tyrosine and tryptophan occurs in the peptide. In addition, downshifted ultraviolet resonance Raman (UVRR) frequencies are observed for the radical state, reproducing spectral downshifts observed for ?2. The frequency downshifts of the ring and CO bands are consistent with charge transfer from YO· to W or another residue. Such a charge transfer mechanism implies a role for the ?2 Y-W dyad in electron transfer.

SUBMITTER: Pagba CV 

PROVIDER: S-EPMC4686667 | biostudies-literature | 2015 Dec

REPOSITORIES: biostudies-literature