Plays an important role in the biosynthesis of the phospholipid phosphatidylcholine (PubMed:12461134, PubMed:19667100). Catalyzes the formation of CDP-choline (PubMed:12461134, PubMed:19667100). CTP + H(+) + phosphocholine = CDP-choline + diphosphate Optimum temperature is 30 degrees Celsius. Phospholipid metabolism; phosphatidylcholine biosynthesis; phosphatidylcholine from phosphocholine: step 1/2. By cold treatment. No visible phenotype under normal growth conditions. Belongs to the cytidylyltransferase family.