***From Wikipedia*** Function In the cell, small molecules such as gases and glucose diffuse to where they are needed. Large molecules synthesized in the cell body, intracellular components such as vesicles, and organelles such as mitochondria are too large (and the cytosol too crowded) to diffuse to their destinations. Most kinesins transport such cargo about the cell by walking unidirectionally along microtubule tracks hydrolysing one molecule of adenosine triphosphate (ATP) at each step. It was thought that ATP hydrolysis powered the kinesin walk but it now seems that the force of binding to the microtubule is what pulls the cargo along while the binding of ATP assists the direction of motion. Structure The typical kinesin is a protein dimer consisting of two heavy chains and two light chains. The heavy chains comprise a globular head (the motor domain) connected via a short, flexible neck linker to the stalk - a long, central coiled-coil region - that ends in a tail region formed with a light-chain. The stalks intertwine to form the kinesin dimer. Cargo binds to the tail while the twin heads alternately bind the microtubule as the kinesin pulls the cargo along. The heads will hydrolyze 2 ATP molecules per step. Polarity Motor proteins travel in a specific direction along a microtubule. This is because the microtubule is polar, the heads only bind to the microtubule in one orientation, and ATP hydrolysis drives the molecule in one direction. Most kinesins walk towards ...
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Wednesday, 22 August 2012
Coast to Coast Am Dec 28 2010 part1
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