Membrane-induced conformational change in human apolipoprotein H

• Published in: Biochemical journal Vol. 348 Pt 1; no. 1; pp. 103 - 106
• Main Authors: Wang, S X, Sun, Y T, Sui, S F
• Format: Journal Article
• Language: English
• Published: England 15.05.2000
• Subjects: beta 2-Glycoprotein I; Cell Membrane - metabolism; Circular Dichroism; Glycoproteins - chemistry; Glycoproteins - drug effects; Glycoproteins - metabolism; Humans; Liposomes - chemistry; Membrane Lipids - metabolism; Methanol - pharmacology; Phospholipids - chemistry; Phospholipids - metabolism; Phospholipids - pharmacology; Protein Conformation - drug effects
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/0264-6021:3480103

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.