Abstract
Active-beta-galactosidase (EC 3.2.1.23) is often formed in rec(-) merozygotes containing a pair of mutations in the z gene of the lac operon. Contrary to expectation, with certain pairs of mutants this enzyme, upon dissociation, does not yield two independent polypeptides but only a single continuous protomer. Both genetic recombination and suppression have been ruled out as the source of this phenomenon. Therefore we believe we are observing the synthesis of one protein from two independently functioning genes.