Measurement of the step size of the molecular motor, dynein

Lawlor, Patrick N.
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At any given time, an enormous number of diff erent events are occurring in every living cell - that cells function predictably and reliably is a testament to nature's superb engineering. One of the most vital components of the cell that aids in the organization and coordination of this hodgepodge is a protein called the molecular motor. Like a man-made motor, the molecular motor converts chemical energy into useful mechanical work (some types even function in reverse). The type of molecular motor that is the subject of this work is called the 'microtubule-based transport molecular motor', the type responsible for shuttling various types cargos around the cell. Many important cargos - vesicles, organelles, large nucleic acid sequences - are far too large to diff use to their targets within the cell on a biologically relevant timescale. Cells divide on the scale of minutes; hours, days, or years can pass before large types of cargo would reliably diff use along the length of some types of cells (e.g., meter-long nerve cells). Because molecular motors provide such an important and pervasive mechanism of transport, their malfunctions have the potential to deleteriously a ect the function of an organism to a high degree. Most human diseases whose causes have been linked to molecular motor malfunction or deficiency are neurological in nature. Molecular motors have been implicated in neurodegenerative diseases such as Huntington's and Alzheimer's diseases, and developmental diseases such as lissencephaly (the condition of the brain lacking folds). Understanding their function is not only an issue of basic science, but one of medical relevance.