Interacting Binding Sites of Isoleucyl-tRNA Synthetase from <em>Escherichia coli</em> Studied by Equilibrium Partition.

The binding of tRNA^Ile to isoleucyl-tRNA synthetase in the presence of isoleucine or ATP was investigated using the equilibrium partition method. Isoleucine decreased the affinity of tRNA^Ile for the enzyme by a factor of about 5. For the free standard energy of interaction a value of about 1 kcal/mol (4.2 kJ/mol) was calculated. ATP exhibits qualitatively the same effect as isoleucine. A binding of two molecules isoleucine per molecule of enzyme could not be demonstrated even in the presence of ATP and pyrophosphatase. [ABSTRACT FROM AUTHOR]