Cold-induced dissociation of tetrameric E. Coli tryptophanase into dimkks

The Effect of Anions and Caations Oll the Dissociation of the Tetrameric Tryptophanase (Tnase) into Dimers Has Been Studied. Dissociation Was Monitored by HPLC Gel Filtration on a Superosel2 Column Holo-Tnase Partialy Dissociates into Dimers in Cold Apo-Tnase Ahnost Completely Dissociates at pH 75 in Tris-0 IM HCI or HNO3 but Does Not Dissociate in Tris-0. IM H3PO4, 0.05M Tricine-KOH and 0. IM Imidazole-hci Buffers. Yet, in Imidazole-0. IM HCt, pH 7.5, 50% Dissociation Occurs. the W330F Mutant Tnase Shows Enhanced Cold Lability. Its Incubation at Zero Deg Centigrade Leads to a Partial Release of Pyridoxal-p and Dissociation into Dimers. Conclusion: Cold Dissociation of Apo-tnase into Dimers Depends on the Nature and Concentration of Anions. the Effect of Different Anions Corresponds to Their Position in the Hofineister Ser. of Salts. Our Results Suggest That Hydrophobic Interactions Play an Important Role in Maintenance of the Active Struct.