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Crystal structure of γ-tubulin complex protein GCP4 provides insight into microtubule nucleation
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Edité par CCSD ; Nature Publishing Group -
International audience. Microtubule nucleation in all eukaryotes involves g-tubulin small complexes (gTuSCs) that comprise two molecules of g-tubulin bound to g-tubulin complex proteins (GCPs) GCP2 and GCP3. In many eukaryotes, multiple gTuSCs associate with GCP4, GCP5 and GCP6 into large g-tubulin ring complexes (gTuRCs). Recent cryo-EM studies indicate that a scaffold similar to gTuRCs is formed by lateral association of gTuSCs, with the C-terminal regions of GCP2 and GCP3 binding g-tubulin molecules. However, the exact role of GCPs in microtubule nucleation remains unknown. Here we report the crystal structure of human GCP4 and show that its C-terminal domain binds directly to g-tubulin. The human GCP4 structure is the prototype for all GCPs, as it can be precisely positioned within the gTuSC envelope, revealing the nature of protein-protein interactions and conformational changes regulating nucleation activity.
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