Helicase: Difference between revisions

Two crystal form of the enzyma, one couple with a 10 mer DNA and a non hydrolizable form of ATP (ATPnP) (pdb id: [[3pjr]], <scene name='User:Luis_E_Ramirez-Tapia/Sandbox_2/3pjrinitial/1'> (Enzyme Subtrate Structure) </scene>and another a truncated form embebed in sulfate (pdb id: [[2pjr]]<scene name='User:Luis_E_Ramirez-Tapia/Sandbox_2/2pjrinitial/1'> (Enzyme Product Structure)</scene>, give a light in a model for how ATP hydrolysis results in motor movement along ssDNA. In the figure below step 1 (top) is the ATP free (product) ssDNA conformation. The DNA bases are labelled arbitrarily. On binding ATP, F626 creates a new binding pocket for base 6. Likewise, F64 destroys an acceptor pocket for base 2, forcing it to move to the position occupied by base 1. After ATP hydrolysis, the grip on base 6 is released. When the Y257 pocket is re-opened due to movement of F64, bases 3-6 can now flip through the acceptor pockets to their new positions. This model predicts that each ATP hydrolysis event will advance PcrA one base along ssDNA.[http://www.icnet.uk/labs/wigley/projects/helicase/35.html]