Purification by immunoadsorbtion chromatography of the normal and a mutant form of the B2 subunit of Escherichia coli tryptophan synthase.

Columns containing immobilized immunoglogulin G fractions from normal and immunized animals were used to purify the wild-type beta component of Escherichia coli tryptophan synthase, formula alpha2 beta2, and a mutant form of the beta component. The procedure yielded proteins with no detectable contaminants as measured by analytical acrylamide disc gel electrophoresis and immunodiffusion against proteins subject to sodium dodecylsulfate acrylamide electrophoresis. After elution from the antibody column at pH 11 the normal beta component, by dialysis against pyridoxal phosphate at pH 7.5, could be restored to the enzymatically-active beta2 dimer with a specific activity of 1700 enzyme units/mg protein. This compares with reported values of 2500-3000 enzyme units/mg when the beta2 dimer is purified by conventional means.