THE POSITION OF THE HETEROLOGOUS DOMAIN CAN INFLUENCE THE SOLUBILITY AND PROTEOLYSIS OF BETA-GALACTOSIDASE FUSION PROTEINS IN ESCHERICHIA-COLI

The VPI protein (23 kDa) of the foot-and-mouth disease virus has been produced in MC1061 and BL21 E. coli strains as beta-galactosidase fusi on proteins, joined to either the amino and/or the carboxy termini of the bacterial enzyme. In BL21, devoid of La protease, all the recombin ant fusion proteins are produced at higher yields than in MC1061, and occur mainly as inclusion bodies. The fusion of VP1 at the carboxy ter minus yields a protease-sensitive protein whose degradation releases a stable, enzymatically active polypeptide indistinguishable from the n ative beta-galactosidase. On the contrary, when the same viral domain is fused to the amino terminus, the resulting chimeric protein is resi stant to proteolysis even in the soluble form. These data demonstrate that the position of the heterologous domain in beta-galactosidase fus ion proteins would not be irrelevant since it can dramatically influen ce properties of biotechnological interest such as solubility and prot eolytic resistance.