Purification and characterization of a protein capable of binding to fatty acids and bile salts in Giardia lamblia.

A specific fatty acid binding protein was isolated from Giardia lamblia, using an affinity column with butyric acid acting as a ligand in place of stearic acid. This method has proved to be more efficient than the one previously described using stearic acid as ligand. The purified fraction showed 8 electrophoretic bands of proteins, with molecular weights ranging between 8 and 80 kDa. This pattern is a consequence of the aggregation of a protein with a molecular weight of 8,215 Da, corresponding to the lower molecular weight band, the only one capable of binding to fatty acids. The labeled oleic acid bound to these purified proteins was replaced by a 100-fold greater concentration of taurocholate, glycocholate, deoxycholate, palmitic acid, and arachidonic acid, having a greater displacement of the bile salts than the free fatty acids.

Binding properties and immunolocalization of a fatty acid-binding protein in Giardia lamblia.

We describe here a fatty acid-binding protein (FABP) isolated and purified from the parasitic protozoon Giardia lamblia. The protein has a molecular mass of 8 kDa and an isoelectric point of 4.96. A Scatchard analysis of the data at equilibrium revealed a dissociation constant of 3.12 x 10(-8) M when the labeled oleic acid was displaced by a 10-fold greater concentration of unlabeled oleic acid. Testosterone, sodium desoxycholate, taurocholate, metronidazol, and alpha-tocopherol, together with butyric, arachidonic, palmitic, retinoic, and glycocholic acids, were also bound to the protein. Assays with polyclonal antibodies revealed that the protein is located in the ventral disk and also appears in the dorsal membrane, the cytoplasm, and in the vicinity of the lipid vacuoles.