cct functions as a dimer of either α and β subunits encoded by "pcyt1a" and "pcyt1b", respectively. cctα has four domains; a nuclear localization signal (nls), an α-helical membrane binding domain, a catalytic domain, and a phosphorylation domain. the major difference between the α and β isoforms is that cctβ lacks the nls resulting in a predominantly cytosolic pool of cctβ. on the other hand, the presence of an nls results in a predominantly nuclear pool of cctα. cctα shuttles between the nucleus (where it is considered inactive) to the cytoplasm where it associates with membranes and is activated in response to lipid activators or during progression through the cell cycle when pc demand is high.