cellbio - 11/28-11/30 - 100-200 uM actin monomers...

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11/28-11/30 - 100-200 uM – actin monomers spontaneous nucleation would be a problem - Profilin – small protein; binds to actin monomers on corner – enough to saturate every monomer however can’t bind to polymer – inhibits spontaneous nucleation - actin ATP hydrolysis - ADF/Cofilin – actin depolimerizing factor - binds both monomers and polymers, will not bind if ATP is bound - likes to bind ADPPi filaments - recycling – ADF breaks the filament to chunks and eventually into individual monomers - Prolifin binds ADP/ATP monomers – ADF/Cofilin - is a nucleotide exchange factor for actin monomers - Profilin dissociates filament after monomer addition - growth at the front, disassembly at the back - capping protein – binds to barbed end, capping growth (don’t want filament to get too long because it will become ineffective) - too much capping protein will inhibit growth, too little will result in ineffective filaments (long and floppy) - need a medium – 2.5uM – allows filament growth - cross-linking proteins - alpha actin – will make filament network stronger - head is flexible - Fimbrin – head not flexible - Spectrin – monomenc – skeletal muscle - motor proteins - Myosin - riger mortis – no ATP for Myosin II - rigor – no nucleotide and tight binding - ATP binding rouses dissociation of PAM. ATP hydrolysis causes movement of the head forward - ADPi myosin rebinds one step forward - actin binding p dissociation - phosphate release causes the force producing power stroke - after power stroke, ADP dissociates - rigor - Myosin II - processivity – ability to move along substrate a long time before falling off - duty cycle – fraction of life spent bound to substrate - muscle myosin – thick and thin filaments - tropomodulin – caps the pointed end - Cap Z – on Z line binds to barbed end (capping protein) - tropomyosin/troponin - inhibits actin myosin interaction by filling the groove – bound to troponin complex of 3 - Ca+ influx binds to C subunit of troponin which causes tropomyosin to move out of the groove - microtubules – built out of tubulin alpha-beta - binds GTP - only hydrolyzed in polymene state – grows in positive direction - beta can be bound to GTP or GDP guest lecturer - it GTP-tubulin only at positive end? - tubulin superfamily - alpha tubulin (alpha 1-7) – alpha 1A(brain specific); alpha 4A(testes specific) - beta tubulin (beta 1-8) – beta 3(neuron specific) also in cancer cells - gamma tubulin – enriched at the centrosome “tubulin nucleator” - template and protofilament models - TuRC may be a pausing factor - delta, epsilon, zeta - tubulin (alpha/beta) and microtubule post-translational modifications - tyrosination/detyrosination – C-terminus of alpha-tubulin - deta2 modification – C-terminus of alpha-tubulin - acetylation – lysine 40 of alpha-tubulin - polyglycylation – C-terminal alpha and beta tubulin - polyglutamylation – C-terminal alpha and beta tubulin - phosphorylation and palmitoylation - location of polyglutamylation in the dimmer and polymer
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This note was uploaded on 02/29/2012 for the course ZOOLOGY 570 taught by Professor Stretton during the Fall '10 term at Wisconsin.

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cellbio - 11/28-11/30 - 100-200 uM actin monomers...

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