Catalyzes the key rate-limiting step in the CDP-choline pathway for phosphatidylcholine biosynthesis. CTP + H(+) + phosphocholine = CDP-choline + diphosphate Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphatidylcholine from phosphocholine: step 1/2. Most of its activity is membrane-associated. Present with 3050 molecules/cell in log phase SD medium. Belongs to the cytidylyltransferase family.