Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Mo Chen
1, Lintao Bu
2, Markus Alahuhta
3, Roman Brunecky
3, Qi Xu
3, Vladimir V. Lunin
3, John W. Brady
4, Michael F. Crowley
3, Michael Himmel
3 and
Yannick J. Bomble3, (1)Molecular Biology and Genetics, Cornell University, Ithaca, NY, (2)National Bioenergy Center, National Renewable Energy Laboratory, Golden, CO, (3)Biosciences Center, National Renewable Energy Laboratory, Golden, CO, (4)Department of Food Science, Cornell University, Ithaca, NY
Family 48 cellulases are essential components in several biomass-degrading bacteria. CelS (GH48) and CelA (GH48/GH9), for example, are the most prevalent cellulases in
C. thermocellum and C. Bescii, respectively. Recent studies have shown that the deletion of CelS reduces the activity of
C. thermocellum by more than 50% and that CelA is responsible for most of the cellulolytic activity in
C. Bescii. Therefore, understanding and improving these cellulases, and ultimately the corresponding microbes, are essential steps in improving the CBP process.
Recent crystallographic protein structures solved in our group have highlighted key differences in the structures of several GH48s. Some of these differences are located at the exit of the catalytic tunnel and may explain the range of activities exhibited by these cellulases.
Here we study the difference in product expulsion in four GH48s from C. cellulolyticum (CelF), C. thermocellum (CelF), C. bescii (CelA), and B. pumilus (Cel48). Steered molecular dynamics simulations and the Jarzynski equality are used to calculate the binding free energies of cellobiose in the catalytic tunnel. Additionally, based on the comparison of the SMD pulling trajectories for these four structures; several point mutations on the key binding residues were made computationally in CelF and CelA to study the free energy changes during the product expulsion process.
