cDNA cloning and tissue-specific expression of the phosphatidylcholine transfer protein gene

We have isolated a cDNA containing the complete coding sequence of bovine liver phosphatidylcholine transfer protein (PC-TP). The deduced amino acid sequence consists of 213 amino acid residues and is, except for a lysine instead of an arginine at position 167, identical to the sequence determined by Edman degradation [Akeroyd, Moonen, Westerman, Puyk and Wirtz (1981) Eur. J. Biochem. 114, 385-391]. A cDNA encoding amino acid residues 41-214 of mouse lung PC-TP was also isolated. The predicted amino acid sequence was 90% similar (81% identical) to the corresponding sequence of bovine liver PC-TP, demonstrating that PC-TP is conserved among mammalian species. By Southern blot analysis, evidence was obtained for the presence of a single bovine PC-TP-encoding gene. The expression of the PC-TP gene was determined during mouse embryonic development and in adult mouse tissues using an RNase protection assay. PC-TP RNA was present in embryos at all stages of development as early as the embryonic stem cell, suggesting a role for PC-TP in cell growth and differentiation. Towards the end of embryonic development, just before term, high levels of PC-TP RNA were found in the liver. This level was even higher 7 days post-term. In addition to adult liver, high levels of PC-TP RNA were also found in kidney and testis. The prominent presence of PC-TP in developing and adult liver is compatible with its proposed role in bile formation.