Cloning and structure analysis of the rat apolipoprotein A-I cDNA

Apolipoprotein A-I, the major protein in mammalian high-density lipoprotein, acts as a cofactor for lecithin-cholesterol acyltransferase during the formation of cholesterol ester and as such, is thought to promote cholesterol efflux from peripheral cells to the liver. In this paper, we report the partial purification of rat liver apolipoprotein A-I mRNA by a polysome immunoadsorption technique, and its cDNA cloning. Isolation of two overlapping cDNA clones enabled us to derive the whole rat apolipoprotein A-I cDNA coding sequence. Comparison of the deduced protein sequence with its human counterpart reveals a striking homology between the prepropeptide precursors. Both mature protein amino-terminal regions are very homologous, suggesting that this particular domain could be involved in lipid/protein binding or lecithin-cholesterol acyltransferase activation.