Nicking of the tryptophan synthase β2-subunit at Glu-296 prevents the conformational change undergone on binding the α-subunit

Using a monoclonal antibody as conformational probe it has been shown that the weakly active nicked-β2 dimer of tryptophan synthase generated by proteolytic cleavage at Glu-296, does not undergo on association with α subunit a conformational change known to occur in intact β2 subunit. This α induced conformational change is also prevented in intact β2 by the coenzyme pyridoxal-5'-phosphate when the substrate l-serine is absent.