OCCURRENCE OF HISTONE-RELATED OXALATE BINDING IN RAT-LIVER NUCLEUS

The rat liver nuclear oxalate binding protein was isolated, purified b y anion and cation exchange column chromatography using Diethyl Amino Ethyl Sephadex, Carboxy Methyl Cellulose and Carboxy Methyl Sephadex C -50 ion exchangers. The purified oxalate binding protein was found to be H1B of H1 fraction of histones. Kinetic analysis of oxalate binding showed the presence of two affinity sites, one with Kd of 133.5 nM an d Bmax of 40 pmoles and another with Kd of 262.5 nM and Bmax of 210 pm oles. The optimal oxalate binding was at pH 4.2 and at 28 degrees C. T he oxalate binding was specific and reversible and not due to ionic ch arge interaction. The IC50 of other dicarboxylates was higher than tha t of oxalate. EGTA had no effect on oxalate binding but di- and tri-ca rboxylate carrier inhibitors and thiol modifying agents significantly lowered the binding activity. Oxalate binding to histones was signific antly reduced in the presence of DNA or nucleotides, but RNA had no ef fect. ATP completely inhibited the oxalate binding activity at 1 mM co ncentration. Different tissues exhibited oxalate binding showing ubiqu itous nature. Calf thymus H1 showed maximal binding similar to liver h istones.