title: Isolation and partial characterization of the inactive and active forms of human plasma phospholipid transfer protein (PLTP).
abstract: Plasma phospholipid transfer protein (PLTP) plays an important role in lipoprotein metabolism. Two forms of PLTP exist in human plasma, one catalytically active (high activity form, HA-PLTP) and the other inactive (low activity form, LA-PLTP) (Oka, T., Kujiraoka, T., Ito, M., Egashira, T., Takahashi, S., Nanjee, N. M., Miller, N. E., Metso, J., Olkkonen, V. M., Ehnholm, C., Jauhiainen, M., and Hattori, H. (2000) J. Lipid Res. 41, 1651-1657). The two forms are associated with macromolecular complexes of different size. The apparent size of LA-PLTP is 520 kDa and that of HA-PLTP is 160 kDa. Of the circulating PLTP mass only a minor portion is in the HA-PLTP form in normolipidemic subjects. In the present study we have isolated and partially characterized the LA and HA forms of PLTP. Both LA- and HA-PLTP bind to heparin-Sepharose and can be separated by elution with 0-0.5 m NaCl gradient, with HA-PLTP displaying higher affinity for the matrix. LA-PLTP was further purified using hydrophobic butyl-Sepharose and anti-PLTP immunoaffinity chromatography steps. HA-PLTP was subjected to a second heparin-Sepharose step and hydroxylapatite chromatography. Analysis of the two forms of PLTP by SDS-PAGE, Western blotting, immunoprecipitation, and gel filtration demonstrates that LA-PLTP is complexed with apoA-I whereas HA-PLTP is not. Instead, HA-PLTP copurified with apoE. Based on these findings we suggest a model in which nascent PLTP enters the circulation as a high specific activity form not associated with apoA-I. During or after the transfer of lipolytic surface remnants to HDL, PLTP is transferred to apoA-I-containing HDL particles and thereby becomes part of the low activity complex.
authors.affiliation: Department of Molecular Medicine, National Public Health Institute, Biomedicum, P. O. Box 104, Helsinki FIN-00251, Finland.
authors.forename: Minna
authors.initials: M
authors.lastname: Kärkkäinen
authors.forename: Tomoichiro
authors.initials: T
authors.lastname: Oka
authors.forename: Vesa M
authors.initials: VM
authors.lastname: Olkkonen
authors.forename: Jari
authors.initials: J
authors.lastname: Metso
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hattori
authors.forename: Matti
authors.initials: M
authors.lastname: Jauhiainen
authors.forename: Christian
authors.initials: C
authors.lastname: Ehnholm
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000097:blood; D008565:Membrane Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids / Q000378:metabolism; D010956:Plasmapheresis
chemical_list: D002352:Carrier Proteins; D008055:Lipids; D008074:Lipoproteins; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D010743:Phospholipids