SYNERGISM BETWEEN THE CELLULOSOME-INTEGRATING PROTEIN CIPA AND ENDOGLUCANASE CELD OF CLOSTRIDIUM-THERMOCELLUM

The cellulosome-integrating protein CipA of Clostridium thermocellum w as produced from a recombinant clone of Escherichia coli and purified by cellulose affinity and anion exchange chromatography. Two active fo rms of C. thermocellum endoglucanase CelD were tested for binding and hydrolytic activity on Avicel in the presence and in the absence of Ci pA. One was 68 kDa CelD, which contains an intact dockerin domain. The other was 65 kDa CelD, in which the dockerin domain is partially dele ted. CipA promoted quantitative binding of 68 kDa CelD to Avicel and e nhanced its Avicelase activity by at least ten-fold. By contrast, CipA had no effect on the activity nor on the cellulose-binding affinity o f the truncated 65 kDa form. These results show that interaction betwe en CipA and the catalytic component CelD is needed for the degradation of cellulose and confirm that the interaction is mediated by the dock erin domain of CelD. (C) 1997 Elsevier Science B.V.