Clostridium thermocellum interaction

Within the cellulosome complex, type I dockerin domain is responsible for incorporating its associated glycosyl hydrolase in the bacterial cellulosome via interaction with a reception domain, the cohesin domain. The three-dimensional solution structure of the 69-residue dockerin domain from the thermophilic Clostridium thermocellum (Topt = 55-65 °C) was solved by NMR and was found to consist of two Ca " -binding loop-helix motifs connected by a linker. Each Ca " -binding subdomain is stabilized by a cluster of buried hydrophobic sidechains. Recently, the NMR sequence-specific resonance assignment of type II cohesin module from C. thermocellum has been published. ... 

The T. reesei enzymes could also be cleaved into separate domains by proteolysis, and this was discussed elsewhere (Claeyssens, M., and Tomme, P., this volume). Suffice it to emphasize here that the genes encoding cellulases in C. fimi and T. reesei appear to have arisen by domain shuffling and that the enzymes they encode appear to interact with cellulose in a comparable manner, i.e., a catalytic domain is held on the substrate by a binding domain. Cellulases from the bacterium Clostridium thermocellum also contained sequences analogous to Pro-Thr boxes as well as highly conserved carboxyl terminal sequences (2,17,18). It remains to be seen if they have functional organizations similar to those of the C. fimi and T. reesei enzymes. 

Pages, S., A. Belaich, J. R Belaich, E. Morag, R. Lamed, Y. Shoham, and E. A. Bayer. 1997. Species-specificity of the cohesin-dockerin interaction between Clostridium thermocellum and Clostridium cellulolyticum Prediction of specificity determinants of the dockerin domain. Proteins 29 517-27. 

Machado, J Araujo, A Pinto, R Gama, FM. Studies on the interaction of the Carbohydrate Binding Module 3 from the Clostridium thermocellum CipA scaffolding protein with cellulose and paper fibres. Cellulose, 2009, accepted. 

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