Immunoprecipitation of lipid transfer protein activity by an antibody against human plasma lipid transfer protein-I.
Two lipid transfer proteins, designated lipid transfer protein-I (Mr 69 000) and lipid transfer protein-II (Mr 55 000), each of which facilitates the transfer of radiolabelled cholesteryl ester, triacylglycerol and phosphatidylcholine between plasma lipoproteins, were purified from human plasma. Immunoglobulin G was prepared from goat antiserum to human lipid transfer protein-I (i.e., anti-human LTP-I IgG). The progressive addition of anti-human LTP-I IgG to buffered solutions containing either a highly purified mixture of human lipid transfer protein-I and lipid transfer protein-II, or highly purified rabbit lipid transfer protein (Abbey, M., Calvert, G.D. and Barter, P.J. (1984) Biochim. Biophys. Acta 793, 471-480) resulted in specific immunoprecipitation and the removal of increasing amounts, up to 100%, of cholesteryl ester, triacylglycerol and phosphatidylcholine transfer activities. However, similar precipitation studies on human and rabbit lipoprotein-free plasma resulted in the progressive removal of all cholesteryl ester and triacylglycerol transfer activities but only 30% (human) or 20% (rabbit) of phosphatidylcholine transfer activity. In all cases more anti-human LTP-I IgG was required to precipitate rabbit lipid transfer activity than human lipid transfer activity. These results suggest that lipid transfer protein-I and lipid transfer protein-II have antigenic sites in common, allowing precipitation of both proteins by specific antibody to lipid transfer protein-I. Most plasma phosphatidylcholine transfer activity is mediated by a protein (or proteins) other than lipid transfer protein-I and lipid transfer protein-II. In lipoprotein-free plasma all cholesteryl ester and triacylglycerol transfer activity, and some phosphatidylcholine transfer activity, is mediated by lipid transfer protein-I (or lipid transfer protein-I and an antigenically similar protein, lipid transfer protein-II.
Abbey
M
M
Bastiras
S
S
Calvert
G D
GD
D000818:Animals; D000906:Antibodies / Q000302:isolation & purification; D000918:Antibody Specificity; D002352:Carrier Proteins / Q000097:blood* / Q000145:classification / Q000276:immunology; D011232:Chemical Precipitation; D002788:Cholesterol Esters / Q000302:isolation & purification; D002848:Chromatography, DEAE-Cellulose; D000939:Epitopes; D006041:Goats; D006801:Humans; D007120:Immunochemistry; D007074:Immunoglobulin G / Q000302:isolation & purification; D007525:Isoelectric Focusing; D011817:Rabbits
D000906:Antibodies; D002352:Carrier Proteins; D002788:Cholesterol Esters; D000939:Epitopes; D007074:Immunoglobulin G; C030363:lipid transfer protein