Identification of caveolin-1 as a fatty acid binding protein

In an attempt to identify high affinity, fatty acid binding proteins presen t in 3T3-L1 adipocytes plasma membranes, we labeled proteins in purified pl asma membranes with the photoreactive fatty acid analogue, 11-m-diazirinoph enoxy[11-H-3]undecanoate. A single membrane protein of 22 kDa was covalentl y labeled after photolysis. This protein fractionated with caveolin-1 conta ining caveolae and was immunoprecipitated by an anti-caveolin-1 monoclonal antibody. Furthermore, 2D-PAGE analysis revealed that both the alpha and be ta isoforms of caveolin-1 could be labeled by the photoreactive fatty acid upon photolysis, indicating that both bind fatty acids. The saturable bindi ng of the photoreactive fatty acid suggests caveolin-1 has a lipid binding site that may either operate during intracellular lipid traffic or regulate caveolin-1 function. (C) 1999 Academic Press.