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CBNS 101 lecture6 - Motor proteins and Muscle Contraction...

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Motor proteins and Muscle Contraction http://www.m-w.com/mw/art/muscle.gif
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The three classes of cytoskeletal filaments 3 classes of separate protein polymers Microtubules Microtubules emanate from the centrosome, which is often located near the nucleus. Determine the position of membrane-enclosed organelles and direct intracellular transport Intermediate Filaments IFs extend throughout the cytoplasm and form a lamina beneath the nuclear membrane. Provide mechanical strength and resistance to share stress Microfilaments tend to be organized into networks associated with the cell periphery (cortex). Determine the shape of the cell s surface and are necessary for whole- cell locomotion Microfilaments Actin filaments
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Major accessory proteins of the microtubules cytoskeleton Accessory proteins modify the dynamic of the cytoskeletal filament
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Some of the major accessory proteins of the actin cytoskeleton
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The γ -tubulin ring complex is thought to form a platform that allows new microtubules to readily assemble. Microtubules are nucleated from a protein complex containing γ -tubulin The Microtubules organizing center (MTOC) or centrosome
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Actin Filaments assembly and organization are controlled by a large group of actin binding proteins Nucleation catalyzed by a complex of proteins : Actin-related proteins or ARPs ARP complex nucleate Actin filaments growth from the minus end allowing elongation at the plus end
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Microtubules assembly and organization are controlled by additional cellular proteins In response to cell signaling pathways, stathmin bind free tubulin and blocks assembly, resulting in increased rate of MT catastrophe. Once Cytoskeletal filaments have been nucleated they elongate by the addition of soluble subunit. Monomer concentration is usually high in the cell (50-200uM) The pool contains specific proteins that bind to the monomer making polymerization less favorable
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Thymosin and profilin are abundant proteins that bind to actin monomers to regulate the elongation Regulation by signal transduction pathway Actin Filaments assembly and organization are controlled by a large group of actin binding proteins
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Microtubule associated proteins (MAPs) Filaments associated proteins used their binding energy to stabilized or destabilized filaments Protein that bind along the side of the microtubules are call Microtubule associated proteins (MAPs).
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Microtubule associated proteins (MAPs) Several MAPs such as Tau or MAP2 include multiple copies of tubulin Binding motif MAPs are target of several kinases and the resulting phosphorylation can control microtubule activity and its localization in the cell Localisation of MAPs in Axon and dendrites of a Neuron Tau (Green ) confined to the axon MAP2 (Orange) confined to the cell boby and the dendrites
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Actin Filaments assembly and organization are controlled by a large group of actin binding proteins Arrangement of actin filaments
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