| Abstract: | The elution of staphylococcal nuclease on thymidine 3'-(p-Sepharose-aminophenyl phosphate) 5'-phosphate (nucleotide ligand of nuclease covalently bound to Sepharose 4B) was studied in the presence of a variety of soluble nucleotide ligands. The elution volumes of nuclease vary proportionally with matrix-bound ligand concentration (at constant soluble ligand concentration), inversely with soluble ligand concentration (at constant matrix-bound ligand concentration), and inversely with dissociation constant of soluble ligand (at constant concentrations of soluble and matrix-bound ligand). The variation of elution volume was related to an expression which described the competition of soluble and matrix-bound ligand for nuclease binding. Using this expression, values for dissociation constants were derived for nucleotide ligands in both the soluble and bound form. The values for soluble ligand were found to correspond closely to those obtained by either equilibrium dialysis or kinetics of inhibition of nuclease activity. Furthermore, a close correspondence was found between the values of dissocation constants for matrix-bound and soluble thymidine 3'-(p-aminophenyl phosphate) 5'-phosphate, thus defining the interaction of nuclease with the matrix-bound ligand as a process quite similar to that occurring in solution. |
