Endonexin (annexin IV)-mediated lateral segregation of phosphatidylglycerol in phosphatidylglycerol/phosphatidylcholine membranes.

摘要: Endonexin (annexin IV) is a member of the annexin family homologous proteins that share ability to bind pure lipid membranes and aggregate vesicles in Ca(2+)-dependent fashion. appears preferentially interact with certain types lipids such as phosphatidylglycerol (PG) PG/phosphatidylcholine (PC) mixed membranes. Such preferential binding should result localization PG membrane regions where endonexin bound. This was tested using derivative containing fluorophore pyrene, which exhibits fluorescence sensitive molecular collision frequency. Motional restriction pyrene-PG upon endonexin-membrane evident from decreased ratios excimer-to-monomer (E/M) pyrene 97% PG/3% vesicles. A maximum decrease 30% suggests average diffusion constant molecules or 53% assuming only outer-monolayer endonexin. In 5% 10% PC, segregation observed increases E/M 14.2 +/- 1.8% 6.8 0.1%, respectively, presence either 10 mM (5% pyrene-PG) 2 (10% free Ca2+. At higher concentrations Ca2+ (> for > pyrene-PG), smaller endonexin-dependent are at high surface densities compete limited pool pyrene-PG. The nature these interactions systems has implications way annexins may modulate structure cells.