FATTY-ACID-BINDING PROTEIN, A MAJOR PROTEIN IN THE FLIGHT-MUSCLE OF MIGRATING WESTERN SANDPIPERS

Migratory flight in birds is fueled primarily by fatty acid oxidation imposing a requirement for high rates of fatty acid: (a) transport; (b ) uptake; and (c) delivery to intracellular sites of beta-oxidation. M uscle fatty acid binding protein (M-FABP) is a cytosolic protein invol ved in the intracellular transport of fatty acids. Its expression appe ars to be correlated with muscle fatty acid oxidation capacity. The M- FABP was isolated for the first time from a long distance migrant bird using: (i) size exclusion; (ii) anion exchange; and (iii) hydroxyapat ite chromatography. M-FABP has a molecular weight of approximately 140 00 Da and an isoelectric point of pH 4.8. A partial amino acid sequenc e of the protein demonstrated homology to M-FABPs from other species ( 80% identical to human heart FABP). It was estimated that M-FABP compr ises approximately 14 and 21% of total cytosolic protein of the pector alis and heart, respectively; the highest values yet reported from any vertebrate muscle. The abundance of M-FABP in these tissues suggests that the protein may play a key role in fatty acid supply during endur ance flight. Thus, it is proposed that a seasonal increase in M-FABP e xpression could be a component of physiological preparation for migrat ion. (C) 1998 Elsevier Science Inc. All rights reserved.