THE CELLULOSOMEA self-assembling evolutionary marvel

by: Drew Sowersby

Supramolecular Chemistry 5390Dr. Wendi David

Cellulose is the most abundant source of bioenergy on earth

Rubin, E. Nature, 2008, 454, 841-845.

BIOFUELSApplications

Singh, S.; Simmons, B. a; Vogel, K. P. Biotechnology and bioengineering. 2009, 104, 68-75.

The break down of celluloseinvolves 2 major steps

Pretreatment • mechanical (shear)• chemical (ionic, dilute acids)• thermochemical (heat)

Hydrolysis• enzymatic (cellulases) • chemical (strong acids)

switchgrass – before and after ionic liquid pretreatment

Graphic: Wikipedia

Hydrolysis to glucose isachieved via 3 enzymatic steps

http://www.wzw.tum.de/mbiotec/celostruct.htm

The Cellulosome Concept

Bayer and Lamed (1983) Clostridium thermocellum most studied extracellular molecular machine molecular weight of over 2 MDa (2,000,000 Da)

Lamed, R. et al. Biotechnol. Bioeng. Symp., 1983, 13, 163–18.

Characterization of the cellulosome

Complex crystallization

Isothermal calorimetry

Protein purification

Recombinant DNA technology

Bioinformatics and modeling

Electron microscopy

Surface plasmon resonance

Binding

Structure

Composition

What does the research sayabout the cellulosome?

1. Shoham, Y.; Lamed, R.; Bayer, E.A. Trends Microbiol., 1999, 7, 275-281.2. Schwarz, W. H. Appl. Microbiol. Biotechnol. 2001, 56, 634–649.3. Pagès, S. et al. Proteins, 1997, 29, 517–527.4. Carvahlo, A. L. et al. PNAS, 2003, 100, 13809–13814.

Mechanism Cellulosome self-assembly driven by non-specific but highly complementary cohesin/dockerin interactions

Featureso contains18 different dockerin containing enzymes

• cellulases ranging in molecular weights of 40-180 kDa• dockerin is a 23-residue tandemly repeated sequence• dockerin contains 2 calcium binding loop-helix motifs

o cooperative binding by carbohydrate binding modules (CBMs)o binding between dockerin and cohesin is species specifico cohesin is a 9-stranded β - sandwich with a jellyroll topologyo Scaffoldin-cellulase superstructure results in synergistic cellulolytic

activity not seen with free floating cellulases

Scaffoldin and thedockerin-cohesin complex

scaffoldin

Polycellulosomal superstructures

extracellular construction organismal monstrosity resting vs. protracted

• “Plasticity theory”

1. Shoham, Y.; Lamed, R.; Bayer, E.A. Trends Microbiol., 1999, 7, 275-281.2. Bomble, Y. J. et al. J. Biol. Chem., 2011, 286, 5614-5623.

Video Simulation wrap-up

Bomble, Y. J. et al. J. Biol. Chem., 2011, 286, 5614-5623.