InterPro domain: IPR041470

This is the N-terminal domain found in components of the gamma-tubulin complex proteins (GCPs). Proteins containing this domain include spindle pole body (SBP) components such as Spc97 and Spc98 which function as the microtubule-organizing centre in yeast [ 1 ]. Proteins containing this domain also include human GCP4 (Gamma-tubulin complex component 4), which has been structurally elucidated [ 2 ].

Functional studies have shown that the N-terminal domain defines the functional identity of GCPs, suggesting that all GCPs are incorporated into the helix of gamma-tubulin small complexes (gTURCs) via lateral interactions between their N-terminal domains. Thereby, they define the direct neighbours and position the GCPs within the helical wall of gTuRC [ 3 ]. Sequence alignment of human GCPs based on the GCP4 structure helped delineate conserved regions in the N- and C-terminal domains [ 4 ]. In addition to the conserved sequences, the N-terminal domains carry specific insertions of various sizes depending on the GCP, i.e. internal insertions or N-terminal extensions. These insertions may equally contribute to the function of individual GCPs as they have been implied in specific interactions with regulatory or structural proteins. For instance, GCP6 carries a large internal insertion phosphorylated by Plk4 and containing a domain of interaction with keratins, whereas the N-terminal extension of GCP3 interacts with the recruitment protein MOZART1 [ 4 ].

1. Characterization and reconstitution of Drosophila gamma-tubulin ring complex subunits. J. Cell Biol. 151, 1513-24
2. Crystal structure of γ-tubulin complex protein GCP4 provides insight into microtubule nucleation. Nat. Struct. Mol. Biol. 18, 915-9
3. Functional Analysis of γ-Tubulin Complex Proteins Indicates Specific Lateral Association via Their N-terminal Domains. J. Biol. Chem. 291, 23112-23125