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 affinity. They are believed to serve as cytoplasmic transporters of FA and to target FA to specific cellular sites of utilization. Several different FABPs are expressed in neural tissue, including brain FABP (B-FABP), myelin FABP (M-FABP), and heart FABP (H-FABP). We have previously shown that H-FABP transfers FAvia direct collisional interactions with acceptor model membranes. In the present studies, we use a fluorescence resonance energy transfer (FRET) assay to examine the rate and mechanism of transfer of a fluorescent long-chain fatty acid from B-FABP to phospholipid vesicles. The rate of transfer is shown to be independent of buffer ionic strength and dramatically enhanced by the presence of specific anionic phospholipids. These results are consistent with a mechanism by which FA are transferred from B-FABP to phospholipid membranes by a transient collision-based mechanism.