Molecular Motors

    > Any protein that uses ATP hydrolysis to produce a physical force

    > Types:    1.  ATPases that transport ions  [ NaK-ATPase  & H⁺ATPase ]
                        2. enzymes that unwind DNA, etc..   [ helicases, gyrases, topoisomerases ]
                        3. proteins that move vesicles along cytoskeleton [ dyneins & kinesins ]

    > Function:  these intracellular transporters function via ATP hydrolysis,
                         which produces a conformational shift in a globular domain that allows
                         a "walking" movement along a cytoskeletal filament 

                EX:  a.  myosins - thick filaments travel along (pull) thin actin filaments
                        b. kinesins - travel along microtubules
                                                vesicles of neurotransmitters move from cell body
                                                along axon to synaptic knob
                        c. dyneins - connect MT's in cilia & flagella helping them bend in unison 

                            dyneins & kinesins also help spindle assembly, chromosome alignment
                                         and cytokensis

    > Diseases of Motor Proteins:
                missing myosins in cardiac muscle = adult onset hypertrophic myopathy
                mutation of Myosin VI (control stereocilia of ear hair cells) = deafness
                myosin V mutations = coat color changes (lack of melanocyte vesicle transport)
                defective dyneins = retrograde axonal transport & neurodegenerative
                                                 diseases as ALS.
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