Pj. Pussinen et al., MOLECULAR-CLONING AND FUNCTIONAL EXPRESSION OF CDNA-ENCODING THE PIG PLASMA PHOSPHOLIPID TRANSFER PROTEIN, Journal of lipid research, 38(7), 1997, pp. 1473-1481
Humans and the pig show marked similarities in lipoprotein metabolism;
therefore, the pig has been used as a model in numerous nutritional s
tudies. Pig plasma displays no activity of cholesteryl ester transfer
protein (CETP), which is known to be responsible for half of the phosp
holipid mass transfer in human plasma, the other half being accounted
for by the plasma phospholipid transfer protein (PLTP). This makes the
pig an ideal subject for the study of PLTP structure and function. He
re we report the molecular cloning of pig PLTP and the eukaryotic cell
expression of its complementary DNA. Pig PLTP was found to share 93%
amino acid sequence identity with human PLTP and 81% with mouse PLTP.
Tissue expression of PLTP mRNA was examined by a method based on rever
se transcription-polymerase chain reaction (RT-PCR) and solid-phase mi
nisequencing in nine pig tissues. The highest PLTP mRNA levels were fo
und in the pancreas, brain, lung, and liver. Medium from COS-1 cells e
xpressing PLTP possessed phospholipid transfer activity, and the secre
ted recombinant PLTP was detectable by Western blotting in the culture
supernatant. A mutant protein with a substitution of Cys at position
22 by Arg was found to display impaired secretion into growth medium i
ndicating a role for cysteines in the correct folding of PLTP. This st
udy forms the basis for future work on the structure-function relation
ships in pig PLTP.