The Interaction of TOGp with Microtubules and Tubulin

Cynthia Spittle, Sophie Charrasse, Christian Larroque, Lynne Cassimeris
2000 Journal of Biological Chemistry  
TOGp is the human homolog of XMAP215, a Xenopus microtubule-associated protein that promotes rapid microtubule assembly at plus ends. These proteins are thought to be critical for microtubule assembly and/or mitotic spindle formation. To understand how TOGp interacts with the microtubule lattice, we cloned fulllength TOGp and various truncations for expression in a reticulocyte lysate system. Based on microtubule co-pelleting assays, the microtubule binding domain is contained within a basic
more » ... d within a basic 600-amino acid region near the N terminus, with critical domains flanking a region homologous to the microtubule binding domain found in the related proteins Stu2p (S. cerevisiae) and Dis1 (S. pombe). Both full-length TOGp and the N-terminal fragment show enhanced binding to microtubule ends. Full-length TOGp also binds altered polymer lattice structures including parallel protofilament sheets, antiparallel protofilament sheets induced with zinc ions, and protofilament rings, suggesting that TOGp binds along the length of individual protofilaments. The Cterminal region of TOGp has a low affinity for microtubule polymer but binds tubulin dimer. We propose a model to explain the microtubule-stabilizing and/or assembly-promoting functions of the XMAP215/TOGp family of microtubule-associated proteins based on the binding properties we have identified.
doi:10.1074/jbc.m002597200 pmid:10770946 fatcat:5hu7g6kzvrblpeydmcg5k2xsx4