Figure 1.

Structures of human RNR. (A) Each monomer of human α₂ contains three nucleotide-binding sites (PDB: 3HNC, 3HND, 3HNE). The activity-regulating site is housed in the N-terminal cone domain (colored in green). Both the C-terminus and N-terminus are disordered in structures of β₂ (dotted lines, PDB: 2UW2). (B) Crystal structure of human dATP-induced α₆ determined in this study. (C) Scattering from 4 μM α in the presence of 1 mM CDP yields an ab initio shape reconstruction (yellow) that is consistent with the crystal structure of human α₂. (D) Scattering from 4 μM α in the presence of 50 μM dATP and 1 mM CDP yields a shape reconstruction (yellow) that is consistent with the crystal structure of human α₆.