Fig. 1.

Key amino acids along a putative radical transport pathway in class Ia RNR. The pathway is ascertained from docking models of the α2 (gold) and β2 (blue) subunits. Substrate turnover requires charge transfer across α2 and β2 subunits over a distance of 35 Å. Radical hopping via the indicated redox-active amino acids is proposed to account for the observed rate of turnover. Distances are known for proposed hopping steps within individual subunits; distances involving Y356 have not been determined. Graphics were generated from Protein Data Bank entries 1RLR (α2) (16) and 1RIB (β2) (18).