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11 Cards in this Set
- Front
- Back
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Characteristics of Microtubules
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25% of brain proteins
Cell architecture, vesicle trafficking Maintain cell shape and polarity Distribute other filaments Train tracks for vesicles & chromosomes |
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MTOC
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Microtubule organizing center
-centrosomes - neurons and interphase -spindle poles- mitosis -basal bodies |
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Characteristics of Tubulin
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alpha, beta, gamma- for spindle poles
mutliple isotopes of each tubulin Beta units are at the very end |
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Tubulin Synthesis
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alpha binds to beta and then beta can go from gtp to GDP
spiral tubes of tubulin with lumen in center + end grows and reaches out 13 filaments make 1 microtubule |
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In vitro Microtuble assembly
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-form by reversible polymerization of tubulin dimers
I Nucleation- Lag, MTOC serves as nucleation site - dimers associate to form rings -rings uncoil into protofilamets to make a closed tube. |
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SEED
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Nucleus for Assembly = centrosomes
Near the minus end |
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Dynamic instability of Microtubules
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1/2 life = 10 minutes for fibroblast
grow constantly then shrink -Delayed hydrolysis of GTP during MT assembly --During growth, GTP Cap is formed sinces assembly is more rapid than GTP hydrolysis --The cap is stable because it makes subunits more attractive to each other --Once GTP hydrolysis catches up, the cap is lost- catastrophe -- GDP not as strong, depolymerization until recapping |
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Drugs that affect actin
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Chemo drugs,
Phalloidin- bind and stablilize actin filaments cytochalasin- caps actin plus ends swinholide - severs actin filaments latrunculin- binds actin subunits and prevents growth |
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Drugs that affect microtubules
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taxol- bind and stablilize microtubultes
colchicine, colcemid- binds subs and prevent polymer vinblastine, vincristine - "" nocodazole- "" Target rapidly dividing cells |
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Centrosomes
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MTOC that has gamma tubulin
contains centrioles @ 90 pericentriolar material, gamma make it up. microtubules will form its own centrosome but not centriole |
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Microtubtule Associating Proteins - MAPs
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- bind on the MT polymer, stabilize against disassembly
- allow MT to interact with other parts of the cell - Have tubulin binding motifs, targets of kinases -Post translational modicfications of alpha tubulin- acetylation w/ lysine EX tau and MAP2- tau= alzheimers catastrophe factor of kinesin can destabilize |
