The lipid binding site of the phosphatidylcholine transfer protein from bovine liver

✍ Scribed by D. Van Loon; Th.A. Berkhout; R.A. Demel; K.W.A. Wirtz

• Publisher: Elsevier Science
• Year: 1985
• Tongue: English
• Weight: 524 KB
• Volume: 38
• Category: Article
• ISSN: 0009-3084
• DOI: 10.1016/0009-3084(85)90055-6

✦ Synopsis

The phosphatidylcholine transfer protein tPC-TP) from bovine liver has a binding site for phosphatidylcholine (PC). Structural and molecular characteristics of this site were investigated by binding PC-analogues carrying photolabile, fluorescent and short-chain fatty acids. Analysis of the photolabeled PC/PC-TP adduct showed that the hydrophobic peptide segment VaP 7~-Phe-Met-Tyr-Tyr-Phe-Asp 17~ is part of the lipid binding site for the 2-acyl chain. This site was further studied by binding PC carrying cis-parinaric acid at the sn-2-position. Time resolved fluorescence anisotropy measurements indicated that the 2-acyl chain was immobilized following the rotation of PC-TP. Similar experiments with PC carrying cis-parinaric acid at the sn-1-position demonstrated that the 1-acyl chain was immobilized as well but at a site distinctly different from that of the 2-acyl chain. Binding sites for the 1-and 2-acyl chain were then explored by use of PC-isomers carrying decanoic, lauric and myristic acid at the sn-1-~or sn-2-)-position and oleic acid at the sn-2-(or sn-1-)-position. Incubation with vesicles prepared oi these PC-species indicated that binding to PC-TP diminished with decreasing acyl chain length but more so for species with short-chain fatty acids on the sn-2-position than on the sn-l-position. Transfer experiments confirmed that PC-TP discriminates between PC-isomers of apparently equal hydrophobicity favouring the transfer of these species carrying oleic acid at the sn-2-position.