CHARACTERIZATION AND POLYELECTROLYTE PRECIPITATION OF BETA-GALACTOSIDASE CONTAINING GENETIC FUSIONS OF CHARGED POLYPEPTIDES

Genetically engineered versions of beta-galactosidase were constructed through the addition of charged polypeptide fusion tails for the purp ose of enhancing polyelectrolyte precipitation. Negatively charged asp artic acid tails and positively charged poly(arginine) tails were adde d to beta-galactosidase from Escherichia coli. These fusion proteins w ere all shown to possess specific activity equal to that of the native enzyme. Gel permeation and ion-exchange chromatography provided evide nce concerning the integrity of the tails as well as their altered cha rge characteristics. All enzymes containing charged tails displayed en hanced polyelectrolyte precipitation over the native enzyme. An optima l number of charged residues, beyond which no further enhancement of p recipitation was observed, was found to be approximately 10 residues f or each type of tail. No interference from nucleic acids was observed in the precipitation of positively tailed beta-galactosidase.