Molecular insight into γ-γ tubulin lateral interactions within the γ-tubulin ring complex (γ-TuRC).

γ-Tubulin is essential for the nucleation and organization of mitotic microtubules in dividing cells. It is localized at the microtubule organizing centers and mitotic spindle fibres. The most well accepted hypothesis for the initiation of microtubule polymerization is that α/β-tubulin dimers add onto a γ-tubulin ring complex (γTuRC), in which adjacent γ-tubulin subunits bind to the underlying non-tubulin components of the γTuRC.

The IC138 and IC140 intermediate chains of the I1 axonemal dynein complex bind directly to tubulin.

Dyneins are minus end directed microtubule motors that play a critical role in ciliary and flagellar movement. Ciliary dyneins, also known as axonemal dyneins, are characterized based on their location on the axoneme, either as outer dynein arms or inner dynein arms. The I1 dynein is the best-characterized subspecies of the inner dynein arms; however the interactions between many of the components of the I1 complex and the axoneme are not well defined.

IC138 is a WD-repeat dynein intermediate chain required for light chain assembly and regulation of flagellar bending.

Increased phosphorylation of dynein IC IC138 correlates with decreases in flagellar microtubule sliding and phototaxis defects. To test the hypothesis that regulation of IC138 phosphorylation controls flagellar bending, we cloned the IC138 gene. IC138 encodes a novel protein with a calculated mass of 111 kDa and is predicted to form seven WD-repeats at the C terminus.