Monday, April 19, 2010
LL Conference Facility (Hilton Clearwater Beach)
Among the many families of cellulase enzymes contributing to cellulose deconstruction, Cel7A provides most of the hydrolytic potential. Cel7A from T. reesei is thought to align on a broken cellulose chain, pulling the chain out of the ordered cellulose and directing it to the entrance of the active site tunnel, where the cellulose chain is hydrolyzed to cellobiose units. Once the cellulose chain is in position for reaction, the processive mechanism follows a three-step process to continue releasing cellobiose units from the bound cellulose chain: 1) the leading cellobiose unit is cleaved by hydrolysis; 2) the cellobiose unit leaves the tunnel; 3) the cellulose chain advances into the tunnel by a cellobiose unit to the reaction position. In this work we aim to understand the second part of the three-step process. Steered molecular dynamics simulations are used to determine the most probable route of product expulsion and the free energy profile associated with the expulsion process. Several identified protein residues contributing significantly to the interaction energy between the protein and the cellulose unit during the pulling process will serve as potential mutation sites in order to reduce the free energy barrier.