FIGURE 7:

Msps association with the microtubule lattice and plus end affect its function as both a microtubule polymerase and antipause factor. Msps is able to interact with microtubules through 1), plus-end association, 2), addition of tubulin subunits by transient interactions with microtubule end, and 3) association with the microtubule lattice. Msps is an antipause factor that enhances growth and shrinkage of microtubules, as RNAi of Msps leads to an increase in microtubule pause. Msps' ability to enhance either growth or shrinkage is due to its plus-end association and lattice-binding domain, respectively.