Structural and multifunctional properties of cardiac fatty acid-binding protein: from fatty acid binding to cell growth inhibition.

Introduction The cardiac fatty acid-binding protein is one type of a family of nonenzymic proteins [ I , 21 that bind hydrophobic ligands. The localization of these fatty acid-binding proteins (FAHPs) is mainly cytosolic kvith concentrations up to 5% 13 I of soluble proteins. A closer inspection of the subcellular distribution by means of immunohistochemical methods and e.1.i.s.a. [ 41, however. reveals a type-specific compartmentation of FAHPs, e.g. the cardiac-type FAHP is associated with myofibrils and mitochondrial matrix, whereas in hepatocytes the so-called hepatic-type FAHP is associated with the endoplasmic reticulum and the outer membrane of mitochondria [S]. Interestingly, both FAHP types are also found inside the nucleus 14, 51. From the abundance of FAHP in tissues with ‘active’ lipid metabolism and the ability to bind fatty acids with high affinity, an involvement o f these proteins in fatty acid metabolism was inferred. Already in the early days of FAHP research a variety of studies related to this field was undertaken even though the proteins were often not available in pure form and structurally not characterized. With the advent of detailed structural information functions were proposed in a more rationalized manner for the nonenzymic FAHPs, e.g. roles in signal transduction and in regulation of cell growth.