Tuesday, May 3, 2011
Mark R. Nimlos1, Gregg T. Beckham1, Lintao Bu1, Yannick J. Bomble2, James F. Matthews2, William S. Adney2, Mike E. Himmel2 and Michael F. Crowley2, (1)National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, (2)Biosciences Center, National Renewable Energy Laboratory, Golden, CO
Family 1 Carbohydrate Binding Modules (CBMs) are know to preferentially bind
to the hydrophobic faces of crystalline cellulose
1, and it has been proposed that this is due to the hydrophobic face of the protein found in this family. However, interesting and unresolved aspects of this specificity are both the molecular-level reasons for CBMs binding to hydrophobic faces preferentially and how the protein arrives at this surface. For many structures of crystalline cellulose, the hydrophobic crystal faces only represent a minor fraction of the total surface area of the fibril. Adsorption to the other faces of cellulose must then be followed by either desorption and re-adsorption on the correct surface, or movement to the (100) surface.
In this study, we investigate the molecular interaction of the CBM from the Family 7 cellulase (Cel7A) from Trichoderma reesei (or Hypocrea jecorina) on different surfaces of cellulose microfibrils. Molecular Dynamics (MD) simulations show that this CBM does prefer the hydrophobic surface. Compared to the other surfaces of cellulose, the CBM remains more firmly attached to this surface and exhibits less translation and torsion on this surface. In fact, many simulations that started on other surfaces translate to the hydrophobic surface, where they remain bound. The molecular structure and interactions that lead to this specificity will be presented in terms of dynamic simulations and potential energy surfaces.
1J. Lehtiö, J. Sugiyama, M. Gustavsson, L. Fransson, M. Linder, T. T. Teeri Proc. Natl. Acad. Sci., (2003), 100, 484-489.
