Tryptophan synthetase dissociation

Tryptophan synthetase of E. coli, an a 2 P 2 tetramer, can be dissociated into two a subunits and a P 2 subunit (Figure... 

Tryptophan synthetase from E. coli contains two different types of polypeptides which are referred to as a and subunits. The physiologically functional tryptophan synthetase complex consists of two a and two y8 subunits and may be represented by the stylised illustration shown in Fig. 26. Upon dilution the complex dissociates to furnish the a subunits as monomers of mol. wt. 29 000 and a dimer consisting of two j8 subunits, mol. wt. 100000. The dimer contains one pyridoxal phosphate per polypeptide chain. These two components have been separated and used in the study of partial reactions. 

Reversible dissociation and inactivation of tryptophan synthetase by 4.5 M GuHCl at pH 2.3 can be realized. The regain of activity on removal of the denaturant by dilution can reach 90% (Groha et a/., 1978). 

In oligomeric proteins composed of nonidentical subunits, it is possible to determine the functional role of each subunit, if dissociation and isolation of subunits are attained in their native states. Examples are tryptophan synthase, lactose synthetase, and aspartate transcarbamoylase.25 ... 

---