Hibernating mammals rely heavily on lipid metabolism to supply energy during hibernation. We wondered if the fatty acid binding protein from a hibernator responded to temperature differently than that from a nonhibernator. We found that the Kd for oleate of the liver fatty acid binding protein (1.5 micromolar) isolated from ground squirrel (Spermophilus richardsonii) was temperature insensitive over 5-37°C, while the rat liver fatty acid binding protein was affected with the Kd at 37°C being about half (0.8 micromolar) that found at lower temperatures. This same trend was observed when comparing the specificity of various fatty acids of differing chain length and degree of unsaturation for the two proteins at 5 and 37°C. At the lower temperature, ground squirrel protein bound long-chain unsaturated fatty acids, particularly linoleate and linolenate, at least as well as at the higher temperature and matched requirements for these fatty acids in the diet. The most common long-chain fatty acid, palmitate, was a more effective ligand for ground squirrel liver fatty acid binding protein at 5°C than at 37°C, with the opposite occurring in the eutherm. Rat protein was clearly not adapted to function optimally at temperatures lower than the animal's body temperature.Key words: fatty acid binding protein, temperature, hibernation.
Liver Fatty Acid-binding Protein Targets Fatty Acids to the Nucleus