Identification of a Rat 30-kDa Protein Recognized by the Antibodies to a Recombinant Rat Cutaneous Fatty Acid-Binding Protein as a 14-3-3 Protein

Immunoblot analysis with polyclonal antibodies raised against a recombinant rat cutaneous fatty acid-binding protein revealed a 30-kDa protein other than the 15-kDa fatty acid-binding protein in rat skin cytosol. This protein was present in a number of rat organs and in mouse 3T3 L1 cells. The amino acid sequences of the enzymatic peptides of the 30-kDa protein extracted from SDS-PAGE gels suggested that it was a mixture of the subunits of the eukaryotic signaling molecule, 14-3-3 protein. Glutathione S-trans-ferase fusion proteins of 14-3-3 protein subunits were examined for cross-reaction by Western blotting, and the є-subunit alone was found to be immunoreactive, so far as tested. It is likely that the 30-kDa protein detected in the rat tissues by the antibodies is the 14-3-3 protein є-subunit. Although there is no apparent sequence similarity between the fatty acid—binding protein and the 14-3-3 protein subunit, they appear to share a common structural element recognized by the antibodies. Since 14-3-3 proteins and fatty acid—binding proteins are known to interact with a wide variety of cellular proteins, the presence of a common local structure might mutually modulate such interactions.