4.4 - Microtubule-associated motor proteins Kinesins The...

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Microtubule-associated motor proteins Kinesins The First kinesin was isolated as a motor protein responsible for moving vesicles and organelles along nerve axons from the cell body to the synaptic terminals. Composed of 2 light chains and two heavy chains. Heavy chains are entwined to create a stalk region made of coiled alpha-helices.
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Microtubule-associated motor proteins The two globular “heads” of the heavy chains have ATP-binding sites. The heads can bind to microtubules, initiating ATP-ase activity and movement of the kinesin molecule (and cargo) along the microtubule Movement of kinesin only occurs in one direction from the (-) to the (+) end of the microtubules. The “cargo” is bound to the other end of the stalk, the tail region that also contains the light chains. Cargos may include vesicles, protein complexes and organelles, which are bound to specific members of the kinesin family by adaptor proteins (e.g. kinectin)
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Figure 9.16a & b
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The Cytoskeleton Most cells, not just axons, are supported by arrays of microtubules, arranged with their (+) ends pointed away from the center of the cell. Kinesin therefore tends to move organelles in neurons towards the nerve terminal ad in many other cell types towards the edge of the cell, away from the nucleus.
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Dyneins Dyneins another family of microtubule based motor proteins Cytoplasmic dynein is also composed of a dimer of heavy chains with two ATP-binding “heads” and a stalk. Intermediate and light chains surround the
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4.4 - Microtubule-associated motor proteins Kinesins The...

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