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#centrosome

4 public questions tagged with this topic.

Cytoskeleton

The γ-tubulin ring complex (γ-TuRC) functions to:

De novo microtubule formation faces thermodynamic barrier because tubulin dimers inefficiently oligomerize spontaneously requiring template. Gamma tubulin ring complex overcomes this kinetic hurdle by acting as structural template mimicking microtubule end geometry precisely. Complex forms lock washer shape about 30 nm diameter composed of gamma tubulin plus grip motif proteins GCP2 through GCP6 arranged with 13 gamma tubulin copies reproducing geometry of 13 protofilament microtubule plus end. Recruitment to centrosomes and spindle microtubules via pericentrin NEDD1 positions complex with gam

Ref: Kollman et al., Nature 2010 – Gamma TuRC nucleates microtubule formation at minus end template mechanism.

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Cytoskeleton

Which structure serves as the nucleation site for microtubule polymerization in animal cells?

Cytoplasmic microtubule arrays need defined origin to orient trafficking and establish cell polarity and division symmetry. In animal cells primary microtubule organizing center is centrosome positioned near nucleus serving as focal nucleation point and signaling hub. Ultrastructurally centrosome comprises pair of cylindrical centrioles surrounded by amorphous pericentriolar material enriched in coiled coil proteins pericentrin Cep192 and gamma tubulin ring complexes gamma TuRC. Centrioles provide 9 fold symmetry scaffold stabilized by polyglutamylated triplets while PCM concentrates nucleatio

Ref: Doxsey, Nat Rev Mol Cell Biol 2001: Centrosome as nucleation site for microtubule polymerization organization.

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Cell Cycle Regulation

What is the primary function of the γ-TuRC nucleating structure in the centrosome?

Spontaneous microtubule assembly from alpha-beta tubulin heterodimers is kinetically unfavorable due to nucleation barrier requiring oligomeric seed. Centrosomes overcome this via gamma-tubulin ring complex, dominant template in animal cells. Gamma-TuRC assembles as 14 nm wide lock-washer containing about 14 gamma-tubulin molecules positioned with GCP2-6 proteins, namely GCP2, GCP3 forming gamma-TuSC repeats plus GCP4, GCP5, GCP6, plus actin and MZT1/2 small proteins. Structure mirrors 13-protofilament microtubule lattice with minus end capped. Localized within pericentriolar material through

Ref: Kollman et al., Gamma-TuRC Structure and Microtubule Nucleation, Nat Rev Mol Cell Biol 2011; Alberts et al., Chapter 16, Microtubule Organizing Center.

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