Recombinant Drosophila melanogaster Tubulin gamma-1 chain (gammaTub23C)
Description
Overview
The gammaTub23C gene in Drosophila melanogaster encodes gamma-tubulin, a critical component of microtubule-organizing centers (MTOCs). Gamma-tubulin is essential for microtubule nucleation and spindle organization during mitosis and meiosis. Recombinant gammaTub23C refers to the protein produced via heterologous expression systems for functional and structural studies. Its role extends beyond microtubule assembly, influencing spindle orientation, centrosome integrity, and genetic regulation .
Protein Structure
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Domains: Contains conserved GTP-binding motifs and a C-terminal domain critical for interactions with gamma-tubulin ring complex (γ-TuRC) components .
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Post-Translational Modifications: Phosphorylation sites regulate centrosomal localization and activity .
Complex Association
GammaTub23C functions within two primary complexes:
Microtubule Nucleation
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GammaTub23C nucleates microtubules by forming a template at MTOCs, enabling α/β-tubulin polymerization .
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Depletion of γ-TuRC components (e.g., Dgrip128) disrupts spindle assembly but does not abolish γ-TuSC recruitment to centrosomes, suggesting functional redundancy .
Spindle Orientation and Dynamics
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Regulates astral microtubule stability: GammaTub23C stabilizes microtubule plus-ends, ensuring proper spindle positioning via EB1 protein recruitment .
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Mutant studies show mitotic delays, abnormal spindle morphology, and altered microtubule dynamics .
Non-Canonical Roles
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Genetic Regulation: Dominant-negative gammaTub23C alleles interact with chromatin-remodeling genes (e.g., brahma), implying a role in transcriptional regulation .
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Centrosome Structure: Null mutants exhibit fragmented or enlarged MTOCs, indicating structural dependence on gamma-tubulin .
Interaction Network
Key binding partners identified via STRING-db and experimental studies :
| Interactor | Function | Interaction Score |
|---|---|---|
| Dgrip75 | γ-TuRC assembly, centrosome targeting | 0.997 |
| Dgrip91 | γ-TuSC stability, spindle pole integrity | 0.995 |
| Dgrip128 | γ-TuRC-mediated microtubule nucleation | 0.992 |
| Mzt1 | γ-TuRC localization to basal bodies | 0.960 |
| Sas-4 | Centriole assembly, microtubule recruitment | 0.910 |
In Vitro Assembly
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Recombinant γ-TuSC nucleates microtubules at low efficiency compared to γ-TuRC, which forms open-ring structures (~25 nm diameter) for robust nucleation .
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Salt-induced γ-TuRC disassembly into γ-TuSC confirms hierarchical complex formation .
In Vivo Phenotypes
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Mitotic Defects: Homozygous gammaTub23C mutants show mitotic arrest, reduced microtubule density, and aberrant MTOCs .
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Fertility Impact: γ-TuRC depletion in spermatogenesis disrupts meiotic spindle organization and centrosome adjunct formation .
Cell Cycle Regulation
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GammaTub23C associates with chromatin during S phase, potentially influencing DNA replication via PCNA recruitment .
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Mutations in γ-tubulin’s PIP motif delay S-phase progression, linking microtubule dynamics to replication fidelity .
Applications and Implications
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Drug Discovery: Targeting γ-TuRC components could disrupt microtubule dynamics in cancer cells.
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Developmental Biology: Elucidates mechanisms of cell polarity and tissue morphogenesis in Drosophila.
