Characterization of the cellulolytic complex (cellulosome) from Ruminococcus albus

The cellulolytic complex was isolated from the culture supernatant of Rumin ococcus albus strain F-40 grown on cellulose by a Sephacryl S-300IIR column chromatography, The molecular mass of the cellulolytic complex was found t o be larger than 1.5 x 10(6) Da. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that the cellulolytic complex contained at least 15 proteins with molecular weights from 40 kDa to 250 k Da. Among them, II proteins showed endoglucanase and/or xylanase activities on the zymograms. Immunological analysis using an antiserum raised against the dockerin domain of endoglucanase VII of R. albus (DocVII) suggested th at at least 7 proteins in the cellulolytic complex contained a dockerin dom ain immunoreactive with the anti-Doc-VII antiserum, Furthermore, DocVII was shown to specifically interact with a 40-kDa protein of the cellulolytic c omplex by Far-Western blot analysis. These results strongly suggest that th e cellulolytic complex produced by R. albus resembles the cellulosome speci fied for the cellulolytic complex of several clostridia such as Clostridium thermocellum and respective components are assembled into the cellulosome by the mechanism common in all of the cellulolytic clostridia, i.e,, the ce llulosome is formed by the interaction between a dockerin domain of catalyt ic components and a cohesin domain of a scaffolding protein.