Figure 4.

Partial X-ray crystal structure of ScOMPDC complexed with 6-hydroxyuridine 5′-monophosphate (PDB entry 1DQX) superimposed over the structure for unliganded ScOMPDC (PDB entry 1DQW). The movement of the phosphodianion gripper loop (Pro202–Val220) toward the hydrophobic pyrimidine umbrella (Glu152–Thr165) is shown for the unliganded (olive green) and liganded (orange) enzymes. The closure of these loops is cooperative and driven by the formation of a hydrogen bond between the side chains of Gln215 from the “gripper” loop and of Ser 154 from the “umbrella”. Reproduced from ref (29). Copyright 2013 American Chemical Society.