PROPERTIES CONFERRED ON CLOSTRIDIUM-THERMOCELLUM ENDOGLUCANASE CELC BY GRAFTING THE DUPLICATED SEGMENT OF ENDOGLUCANASE CELD

The DNA sequence encoding the duplicated 22 amino acid segment of Clos tridium thermocellum endoglucanase CelD was fused to the 3'-terminus o f the celC gene encoding C. thermocellum endoglucanase CelC. The prese nce of the duplicated segment endowed CelC with the capacity to form c ytoplasmic inclusion bodies containing active enzyme when the hybrid g ene was expressed in Escherichia coli. Inclusion body formation preven ted proteolytic cleavage of the duplicated segment. The intact hybrid protein CelC-Cel'D was purified from inclusion bodies and characterize d. In contrast to CelC, CelC-Cel'D was able to bind to CipA, a protein acting as a scaffolding component of the C.thermocellum cellulase com plex (cellulosome). However, the catalytic properties of CelC-Cel'D we re similar to those of CelC. These results suggest that foreign protei ns tagged with the duplicated segment could be incorporated into the c ellulosome in order to modify the enzymatic properties of the complex. The formation of inclusion bodies by proteins carrying the duplicated segment may also prove a convenient means of purifying cloned gene pr oducts that are sensitive to proteolytic degradation.