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#microtubule-associated protein

2 public questions tagged with this topic.

Cytoskeleton

What is the function of XMAP215?

Microtubule growth in cells exceeds intrinsic tubulin addition rate due to polymerase action of Dis1 ch-TOG XMAP215 family enhancing incorporation efficiency. XMAP215 contains five Tumor Overexpressed Gene TOG domains each with two HEAT repeats capable of binding free alpha beta tubulin dimers with micromolar affinity. Mechanism involves processive tracking: TOG array recruits soluble dimers tethers to plus end via interaction with EB1 and lattice then delivers dimers to growing tip in orientation favoring incorporation increasing growth rate several fold. Function does not require ATP hydroly

Ref: Al-Bassam & Chang, Trends Cell Biol 2011 – XMAP215 polymerase binds tubulin dimers enhances polymerization rate.

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Cytoskeleton

Which microtubule-associated protein (MAP) stabilizes microtubules in neurons?

Microtubule associated proteins of structural type stabilize filaments by binding along walls and bridging protofilaments reducing catastrophe and increasing flexural rigidity. Members include MAP2 and tau families as well as MAP4 sharing homologous microtubule binding repeat domains but exhibiting expression differences: tau enriched in axons MAP2 in dendrites MAP4 broadly in non neuronal tissues and also neurons providing versatility. Tau and MAP2 classically promote assembly and bundling reducing catastrophe promoting rescue and increasing persistence length. MAP4 participates similarly for

Ref: Dehmelt & Halpain, Genome Biol 2005 – MAP family stabilization including MAP4 and MAP2.

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