sentences:  In bacteria, the overall structure is a dimer of two subunits, each consisting of seven α-helices and ten β-strands, with a molecular weight of 23919.13 Da.Orotate phosphoribosyltransferase has a core part plus a flexible loop, which when closed prevents solvent from entering during reaction.In other organisms such as mammals, insects and slime modes it is one of the domains of UMP synthase, with the other being orotidylate decarboxylase.