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16 Cards in this Set
- Front
- Back
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When does movement of centrioles occur?
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During mitosis. DUH
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What is the function of gamma tubulin in centrioles?
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Localizes to the (-) end of MT
Gamma forms open ring template and binds to alpha tubulin in dimer. Determines organization and polarity of MT Low abundance in cell Now thought to bind to protein gamma TURC (Gamma Tubulin Ring Complex) |
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Are centrioles ubiquitous?
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NO.
None in plants or fungi Mouse oocytes dont have centrosomes. Neurons: MT detach from centrosome once formed. |
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What is the function of gamma tubulin in plants?
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Localizes along the length of the MT
May nucleate branches of MT |
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What end is the tubulin added to in MT?
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The (+) end
Fig 9.26 |
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Discuss the growth phase and shortening phase of MT in vitro studies.
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Growth phase is slower than shortening phase.
All phases occur at (+) end Dynamic instability: dynamic behavior of single MT to grow/shrink Model that explains this is called Structural Cap Model of Dynamic Instability |
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Describe MT growth. Fig 9.25
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1. (+) end is an open sheet to which dimers are added.
When dimer is in GTP form: curved structure. Once dimers added to MT structure, they are straight 2. Tube closes up, GTP hydrolysis. 3. During rapid MT gorwth dimers are added faster than spontaneoius closure 4. GTP cap is present: MT dimers in GTP gorm favor the addition of more dimers to the end of MT. GTP tubulin binds GTP tubulin? 5. As MT growth slows or ceases the tube closes completely. Leave the beta tubulin in MT in GDP form, NO GTP CAP. 6. GDP tubulin has different conformations thought to place strain on MT stucutre 7. Without ap of GTP to stablize it there, GTP hydrolysis makes MT unstabe once tube closes. WHAT TUBE? |
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What mechanisms exist to prevent breakdown of MT when GTP hydrolysis makes them unstable?
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Capping proteins at positive end
Embedding MT in the membrane MAPS |
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How can you regulate MT dynamics?
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1. Alter free tubulin concentration
2. Change Ca concentration 3. Capping (+) end, or embed MT in PM 4. MAPS-MT associated proteins -Katanin: severs MT into fragments to expose GDP/Beta subunit ends: catastrophic shrinkage |
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Describe Map1A/Map1B
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Stabilize and promote MT formation
May decrease repulsion of 2 dimers since they bind to (-) areas of tubulin Found in axons and dendrites |
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Describe MAP2/TAU
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MAP2: normal dendritic outgrowth
Tau: mostly axon 1. Accelerate MT polymerization 2. Cross links to other MT: spaces them apart 3. Important in producing axon in nerve cell -if no TAU: no outgrowth |
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Describe MAP4
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Non-brain MAP
1. colocalizes with MT during interphase and mitosis 2. Seems to play role in regulating transport 3. Stabilizes MT arrays 4. May be involved in nucleation. |
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What are the 2 domains of MAPS?
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1. MT binding domain: responsible for stability
2. Projection arm: space MT Spacing is dependent on size/length of projection arm |
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Describe MAP regulation. What are the 2 enzymes known to P MAPS?
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P and deP events
deP must occur for binding 2 enzymes: 1. MAP Kinase 2. Cdc2 Kinase *cell cycle regulators: signaling cascades |
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What are actin monomer polymerizing proteins? (MF dynamics)
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Profilin: binds to actin monomer 1:1 ratio
Binds to monomer: changes the binding cleft for ATP and exchanges ADP for ATP Has higher affinity for actin than thymosin Profilin/actin monomer: added to (+) end only. Once bound to MF, affinity decreases and is released * Controls MF dynamics by availability of thymosins (inhibitory) and profilin (promotory) |
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How can you regulate MF dynamics?
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1. Capping proteins
2. Ca concentration 3. Concentration of actin 4. Over 100 interacting proteins have been found that do this |
