Stabilization of membranes upon interaction of amphipathic polymers with membrane proteins

International audienceAmphipathic polymers derived from polysaccharides, namely hydrophobically modified pullulans, were previously suggested to be useful as polymeric substitutes of ordinary surfactants for efficient and structure- conserving solubilization of membrane proteins, and one such polymer, 18C10, was optimized for solubi- lization of proteins derived from bacterial outer membranes (Duval-Terrie ́ et al. 2003). We asked whether a similar ability to solubilize proteins could also be demonstrated in eukaryotic membranes, namely sar- coplasmic reticulum (SR) fragments, the major protein of which is SERCA1a, an integral membrane protein with Ca2+-dependent ATPase and Ca2+-pumping activity. We found that 18C10-mediated solubilization of these SR membranes did not occur. Simultaneously, however, we found that low amounts of this hydro- phobically modified pullulan were very efficient at preventing long-term aggregation of these SR mem- branes. This presumably occurred because the negatively charged polymer coated the membranous vesicles with a hydrophilic corona (a property shared by many other amphipathic polymers), and thus minimized their flocculation. Reminiscent of the old Arabic gum, which stabilizes Indian ink by coating charcoal particles, the newly designed amphipathic polymers might stabilization of membrane suspensions