Collision-mediated transfer of long-chain fatty acids by neural tissue fatty acid-binding proteins (FABP) - Studies with fluorescent analogs

Mammalian fatty acid-binding proteins (FABP) are a family of intracellular proteins (approx 15 kDa) that bind long-chain fatty acids (FA) with high af finity. They are believed to serve as cytoplasmic transporters of FA and to target FA to specific cellular sites of utilization. Several different FAB Ps are expressed in neural tissue, including brain FABP (B-FABP), myelin FA BP (M-FABP), and heart FABP (H-FABP). We have previously shown that H-FABP transfers FA via direct collisional interactions with acceptor model membra nes. In the present studies, we use a fluorescence resonance energy transfe r (FRET) assay to examine the rate and mechanism of transfer of a fluoresce nt long-chain fatty acid from B-FABP to phospholipid vesicles. The rate of transfer is shown to be independent of buffer ionic strength and dramatical ly enhanced by the presence of specific anionic phospholipids. These result s are consistent with a mechanism by which FA are transferred from B-FABP t o phospholipid membranes by a transient collision-based mechanism.