Specific interaction of rabbit C-reactive protein with phospholipid membranes

C-Reactive protein (CRP) is a major acute phase reactant in most mammalian species. Phosphorylcholine (free PC) is the most effective inhibitor of CRP. Three kinds of lipid were synthesized to study the recognition and binding mechanism of CRP with cells. The synthesized lipids were DS8PC, DS6PC and DP3PC, Between the lipid tails and polar PC group of the synthesized lipid molecules, there is a long-arm spacer of eight, six and three atoms respectively. In the mixed lipid membrane of synthesized lipid and natural distearoyl phosphatidylcholine (DSPC), the PC polar groups of the synthesized lipids protrude out of the membrane. These PC groups may act as CRP receptors in the membrane, The interaction of rabbit CRP with lipid monolayers and liposomes was studied by ellipsometry and fluorescence assay. The experiments show that rabbit CRP can specifically bind with a mixture of DS8PC and DSPC lipid monolayers. It is concluded that steric hindrance affects CRP binding to lipid monolayers; the depth of the PC binding sites of rabbit CRP is estimated to be about 1 nm.