Plays an important role in the biosynthesis of the phospholipid phosphatidylcholine. Catalyzes the formation of CDP-choline. CTP + H(+) + phosphocholine = CDP-choline + diphosphate Optimum temperature is 30 degrees Celsius. Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphatidylcholine from phosphocholine: step 1/2. No visible phenotype under normal growth conditions. Belongs to the cytidylyltransferase family.