Pseudo-merohedral twinning in monoclinic crystals of human orotidine-5′-monophosphate decarboxylase

The crystal structure of orotidine-5′-monophosphate decarboxylase, the C-terminal domain of human UMP synthase, was determined by molecular replacement using data from highly pseudo-merohedrally twinned monoclinic crystals with a ≃ c unit-cell parameters.