CHARACTERIZATION OF THE CELLULOLYTIC COMPLEX (CELLULOSOME) PRODUCED BY CLOSTRIDIUM-CELLULOLYTICUM

The cellulolytic complex was isolated from Clostridium cellulolyticum grown on cellulose. Upon gel filtration, the complex was found to cons ist mainly of 600-kDa units, along with a 16-MDa aggregate, Its abilit y to degrade various substrates and its capacity to bind to the crysta lline cellulose were measured. The results of sodium dodecyl sulfate-p olyacrylamide gel electrophoresis, N-terminal sequencing, and blotting analysis showed that all of the known cellulases of this organism are present in this complex. Three major components were observed: the fi rst component, a noncatalytic, large (160-kDa) protein, was identified based on its ability to bind to the dockerin-containing cellulases as scaffolding protein CipC. The other two components, which had molecul ar masses of 94 and 80.6 kDa, were identified as CelE and CelF, respec tively. The identified cellulases and some other components of the cel lulosome were able to bind to a miniCipC1 construct. In addition to pr oviding an extensive description of the system, the results of the pre sent study confirm that the dockerin-cohesin domain interaction plays an essential role in the constitution of the cellulosome.