Tubulin binding protein that inhibits microtubule nucleation and growth, resulting in shorter microtubules. Homotrimer; self-association is mediated by the N-terminal coiled coil. Interacts with GRID2 and may also interact with GRID1 (By similarity). Interacts with EML3 (PubMed:25740311). Binds unpolymerized tubulins via its WD repeat region (PubMed:11694528, PubMed:24706829). Colocalizes with the microtubule cytoskeleton. Colocalizes with the mitotic spindle. Ubiquitous. Contains a tandem atypical propeller in EMLs (TAPE) domain. The N-terminal beta-propeller is formed by canonical WD repeats; in contrast, the second beta-propeller contains one blade that is formed by discontinuous parts of the polypeptide chain (By similarity). Belongs to the WD repeat EMAP family.