title: Properties of human plasma lipid transfer protein in aqueous solution and at interfaces.
abstract: Human plasma lipid transfer protein (cholesteryl ester transfer protein) has been characterized for its solution and surface properties. The protein is monomeric in aqueous solution up to 0.62 g/L (11.7 microM) as demonstrated by sedimentation equilibrium. It binds to the surface of a lipid microemulsion having an average diameter of 26 nm made from triolein and egg yolk phosphatidylcholine, with an estimated dissociation constant 1.2 x 10(-8) M, and the maximum saturation binding level is 8 protein molecules per particle regardless of the presence of apolipoprotein A-I. Circular dichroism measurement indicated that the protein in solution is predominantly in the beta-sheet/beta-turn conformation with some alpha-helix, and this profile does not undergo drastic change by its binding to the lipid surface. The analysis of the behavior of the protein in its monomolecular layer at the air-buffer interface indicated that it is also monomeric at the interface. LTP molecules occupied the same area per amino acid as other apolipoproteins in the monolayer but had a higher collapse pressure of its monolayer (18 dyn/cm), and the protein stayed at the interface even after the overcompressing monolayer far beyond the collapsing pressure up to 40 dyn/cm.
authors.affiliation: Department of Medicine, University of Alberta, Edmonton, Canada.
authors.forename: T
authors.initials: T
authors.lastname: Ohnishi
authors.forename: L D
authors.initials: LD
authors.lastname: Hicks
authors.forename: K
authors.initials: K
authors.lastname: Oikawa
authors.forename: C M
authors.initials: CM
authors.lastname: Kay
authors.forename: S
authors.initials: S
authors.lastname: Yokoyama
mesh_terms: D016632:Apolipoprotein A-I / Q000378:metabolism / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D053480:Cholesterol Ester Transfer Proteins; D002942:Circular Dichroism; D004655:Emulsions; D006023:Glycoproteins; D006801:Humans; D050356:Lipid Metabolism; D008970:Molecular Weight; D010316:Particle Size; D010713:Phosphatidylcholines; D017433:Protein Structure, Secondary; D012996:Solutions; D013499:Surface Properties; D014304:Triolein; D014867:Water
chemical_list: D016632:Apolipoprotein A-I; C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D004655:Emulsions; D006023:Glycoproteins; D010713:Phosphatidylcholines; D012996:Solutions; D014867:Water; D014304:Triolein