Catalyzes the key rate-limiting step in the CDP-choline pathway for phosphatidylcholine biosynthesis. CTP + H(+) + phosphocholine = CDP-choline + diphosphate By phosphorylation (By similarity). Activated by anionic lipid vesicles and by oleic acid or diacylglycerol-containing phosphatidylcholine vesicles (PubMed:7918629,PubMed:8155650). Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphatidylcholine from phosphocholine: step 1/2. Homodimer. It can interconvert between an inactive cytosolic form and an active membrane-bound form. Brain, placenta, liver, fetal and adult lung. The serine residues of the C-terminus are phosphorylated. The inactive soluble form is stabilized by phosphorylation, the active membrane bound form is promoted by anionic lipids or diacylglycerol, and is stabilized by dephosphorylation (By similarity). Monoubiquitinated by the SCF(FBXL2) complex, leading to proteasomal degradation. The disease is caused by variants affecting the gene represented in this entry. Belongs to the cytidylyltransferase family.