Interactions of myristoylated alanine-rich C kinase substrate (MARCKS)-related protein with a novel solid-supported...

The determination of partition coefficients is crucial for the biochemical analysis of membrane-based processes, but requires tedious procedures. We have facilitated this analysis using a silica gel coated with a single phospholipid bilayer (TRANSIL) as the membranous phase. We demonstrate the validity of this method using MARCKS-related protein, a 20-kDa member of the MARCKS family (an acronym for myristoylated alanine-rich C kinase substrate). The partition coefficients describing the association of unmyristoylated and myristoylated MARCKS-related protein with membranes of different phospholipid composition are in agreement with previous work with vesicles and show that both the myristoyl moiety and the basic effector domain of MARCKS-related protein mediate the binding. However, no significant cooperativity is observed between these two domains. Interestingly, MARCKS-related protein binds to TRANSIL membranes more strongly at temperatures below their phase-transition temperature. Taking advantage of this property, MARCKS-related protein was purified by phase-transition chromatography, loading Escherichia coli lysates on a TRANSIL column at 4 degrees C and eluting MRP at room temperature. In conclusion, TRANSIL is a versatile tool to determine the affinity of compounds for phospholipid membranes and to purify membrane-bound proteins. TRANSIL should also enable functional studies of protein-ligand and protein-protein interactions at the surface of membranes.