The functional and assembly mechanisms of the Cellulosome:
The Cellulosome is a megaDalton complex present in some anaerobic bacteria and fungi, which use it to degrade cellulose to ethanol. Glycoside hydrolases that mediate the hydrolysis of cellulose are relatively inefficient, as the glycosidic bonds are often inaccessible to the active site of the enzymes. Anaerobic organisms use assemblies of cell wall hydrolases, the cellulosomes, to exploit the interactions promoted by close proximity. Many hydrolases that use plant cell wall substrates are modular, comprising catalytic domains appended to one or more noncatalytic Carbohydrate-Binding Modules. CBMs direct the enzyme active sites to their substrates and mediate an intimate and prolonged association between the enzyme and the polysaccharide. This project has started in 2003 from a collaboration with Professor Carlos Fontes (FMV-UTL) and the results are now described in several publications from peer-reviewed scientific journals.
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Joana Brás, Alan Cartmell, Ana Luísa Carvalho, Genny Verzé, Edward A. Bayer, Maria João Romão, Carlos M. G. A. Fontes and Harry J. Gilbert, A cellulase that binds helical and planar conformations of cellulose and displays structural conservation with lytic transglycosylases, PNAS, in press.
Begoña García-Alvarez, Roberto Melero, Fernando Dias, José Prates, Carlos Fontes, Steven Smith, Maria João Romão, Ana Luísa Carvalho, Oscar Llorca, Cryo-EM of a Clostridium thermocellum Mini-Cellulosome Reveals Structural Transitions Between Rigid and Flexible Conformations, J. Mol. Biol., in press.
Carvalho, A. L.; Dias, F. M. V.; Nagy, T.; Prates, J. A. M.; Proctor, M. R.; Smith, N.; Bayer, E. A.; Davies, G. J.; Ferreira, L. M. A.; Romao, M. J.; Fontes, C.; Gilbert, H. J., Evidence for a dual binding mode of dockerin modules to cohesins. PNAS 2007, 104, 3089-3094.
Carvalho, A. L.; Goyal, A.; Prates, J. A. M.; Bolam, D. N.; Gilbert, H. J.; Pires, V. M. R.; Ferreira, L. M. A.; Planas, A.; Romao, M. J.; Fontes, C., The family 11 carbohydrate-binding module of Clostridium thermocellum Lic26A-Cel5E accommodates beta-1,4- and beta-1,3-1,4-mixed linked glucans at a single binding site. J. Biol. Chem. 2004, 279, (33), 34785-34793. doi:10.1074/jbc.M405867200
Carvalho, A. L.; Dias, F. M. V.; Prates, J. A. M.; Nagy, T.; Gilbert, H. J.; Davies, G. J.; Ferreira, L. M. A.; Romao, M. J.; Fontes, C., Cellulosome assembly revealed by the crystal structure of the cohesin-dockerin complex. PNAS 2003, 100, (24), 13809-13814. doi:10.1073/pnas.1936124100