On the molecular origin of charge heterogeneity of rat liver fatty acid-binding protein (Z-protein).

The occurrence of many charge isoforms is known for rat liver fatty acid-binding protein, and this is the major cause of conflicting data on the characterization of the protein. Recently, M. Li and T. Ishibashi (1992, Arch. Biochem. Biophys. 298, 254-258) clearly demonstrated that some charge isoforms are due to bound fatty acids. We found that acidic fraction (DE-III) of rat liver fatty acid-binding protein contained isoaspartyl-105 protein resulted from deamidation and peptide rearrangement at Asn-105. Since DE-III fraction carries mainly arachidonate, this post-translational modification might modulate binding specificity of fatty acid-binding protein.