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. Muscle fatty acid binding protein (M-FABP) is a cytosolic protein involved in the intracellular transport of fatty acids. Its expression appears 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) hydroxyapatite chromatography. M-FABP has a molecular weight of approximately 14,000 Da and an isoelectric point of pH 4.8. A partial amino acid sequence of the protein demonstrated homology to M-FABPs from other species (80% identical to human heart FABP). It was estimated that M-FABP comprises approximately 14 and 21% of total cytosolic protein of the pectoralis 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 endurance flight. Thus, it is proposed that a seasonal increase in M-FABP expression could be a component of physiological preparation for migration.