title: Stopped-flow studies of myelin basic protein association with phospholipid vesicles and subsequent vesicle aggregation.
abstract: When mixed with vesicles containing acidic phospholipids, myelin basic protein causes vesicle aggregation. The kinetics of this vesicle cross-linking by myelin basic protein was investigated by using stopped-flow light scattering. The process was highly cooperative, requiring about 20 protein molecules per vesicle to produce a measurable aggregation rate and about 35 protein molecules per vesicle to produce the maximum rate. The maximum aggregation rate constant approached the theoretical vesicle-vesicle collisional rate constant. Vesicle aggregation was second order in vesicle concentration and was much slower than protein-vesicle interaction. The highest myelin basic protein concentration used here did not inhibit vesicle aggregation, indicating that vesicle cross-linking occurred through protein-protein interactions. In contrast, poly(L-lysine)-induced vesicle aggregation was easily inhibited by increasing peptide concentrations, indicating that it did cross-link vesicles as a peptide monomer. The myelin basic protein:vesicle stoichiometry required for aggregation and the low affinity for protein dimerization suggested that multiple protein cross-links were needed to form a stable aggregate. Stopped-flow fluorescence was used to estimate the kinetics of myelin basic protein-vesicle binding. The half-times obtained suggested a rate constant that approached the theoretical protein-vesicle collisional rate constant.
mesh_terms: D000818:Animals; D002417:Cattle; D008027:Light; D008051:Lipid Bilayers / Q000378:metabolism*; D004676:Myelin Basic Protein / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism*; D012542:Scattering, Radiation
chemical_list: D008051:Lipid Bilayers; D004676:Myelin Basic Protein; D010743:Phospholipids