title: Membrane-induced conformational change in human apolipoprotein H.
abstract: The interaction of apolipoprotein H (Apo H) with lipid membrane has been considered to be a basic mechanism for the biological function of the protein. Previous reports have demonstrated that Apo H can interact only with membranes containing anionic phospholipids. Here we study the membrane-induced conformational change of Apo H by CD spectroscopy with two different model systems: anionic-phospholipid-containing liposomes [such as 1, 2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) and cardiolipin], and the water/methanol mixtures at moderately low pH, which mimic the micro-physicochemical environment near the membrane surface. It is found that Apo H undergoes a remarkable conformational change on interaction with liposomes containing anionic phospholipid. To interact with liposomes containing DMPG, there is a 6.8% increase in alpha-helix in the secondary structures; in liposomes containing cardiolipin, however, there is a 12.6% increase in alpha-helix and a 9% decrease in beta-sheet. The similar conformation change in Apo H can be induced by treatment with an appropriate mixture of water/methanol. The results indicate that the association of Apo H with membrane is correlated with a certain conformational change in the secondary structure of the protein.
authors.affiliation: Department of Biological Sciences and Biotechnology, State Key Laboratory of Biomembrane, Tsinghua University, Beijing 100084, People's Republic of China.
authors.forename: S X
authors.initials: SX
authors.lastname: Wang
authors.forename: Y T
authors.initials: YT
authors.lastname: Sun
authors.forename: S F
authors.initials: SF
authors.lastname: Sui
mesh_terms: D002462:Cell Membrane / Q000378:metabolism*; D002942:Circular Dichroism; D006023:Glycoproteins / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D008563:Membrane Lipids / Q000378:metabolism*; D000432:Methanol / Q000494:pharmacology; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D011487:Protein Conformation / Q000187:drug effects; D053482:beta 2-Glycoprotein I
chemical_list: D006023:Glycoproteins; D008081:Liposomes; D008563:Membrane Lipids; D010743:Phospholipids; D053482:beta 2-Glycoprotein I; D000432:Methanol