ISOLATION AND CHARACTERIZATION OF 2 FATTY-ACID-BINDING PROTEINS FROM MOUSE-BRAIN

Two fatty acid binding proteins (FABPs) were isolated from Swiss Webst er mouse brains. Neither protein cross-reacted with antisera to recomb inant liver L-FABP. One protein, designated brain H-FABP, migrated on tricine sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS -PAGE) as a single band at 14.5 kDa with pI 4.9. Brain H-FABP bound NB D-stearic acid and cis-parinaric acid with K-D values near 0.02 and 0. 5 mu M, respectively. Brain H-FABP cross-reacted with affinity-purifie d antisera to recombinant heart H-FABP. The second protein, mouse brai n B-FABP, migrated on tricine SDS-PAGE gels as a doublet at 16.0 and 1 5.5 kDa with pI values of 4.5 and 4.7, respectively. Brain B-FABP boun d NBD-stearic acid and cis-parinaric acid with K-D values near 0.01 an d 0.7 mu M, respectively. The brain B-FABP doublet was immunoreactive with affinity-purified antibodies against recombinant mouse brain B-FA BP, but not with affinity-purified antibodies against heart H-FABP. [H -3]Oleate competition binding indicated that the two brain FABPs had d istinct ligand binding specificities. Both bound fatty acids, fatty ac yl CoA, and lysophosphatidic acid. Although both preferentially bound unsaturated fatty acids, twofold differences in specific saturated fat ty acid binding were observed. Brain B-FABP and brain H-FABP represent ed 0.1 and 0.01% of brain total cytosolic protein, respectively. In su mmary, mouse brain contains two native fatty acid binding proteins, br ain H-FABP and brain B-FABP.