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J Cell Biol April 28, 2003; 161 (2): 349-58.
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Identification of XMAP215 as a microtubule-destabilizing factor in Xenopus egg extract by biochemical purification.

Shirasu-Hiza M , Coughlin P , Mitchison T .

Microtubules (MTs) polymerized with GMPCPP, a slowly hydrolyzable GTP analogue, are stable in buffer but are rapidly depolymerized in Xenopus egg extracts. This depolymerization is independent of three previously identified MT destabilizers (Op18, katanin, and XKCM1/KinI). We purified the factor responsible for this novel depolymerizing activity using biochemical fractionation and a visual activity assay and identified it as XMAP215, previously identified as a prominent MT growth-promoting protein in Xenopus extracts. Consistent with the purification results, we find that XMAP215 is necessary for GMPCPP-MT destabilization in extracts and that recombinant full-length XMAP215 as well as an NH2-terminal fragment have depolymerizing activity in vitro. Stimulation of depolymerization is specific for the MT plus end. These results provide evidence for a robust MT-destabilizing activity intrinsic to this microtubule-associated protein and suggest that destabilization may be part of its essential biochemical functions. We propose that the substrate in our assay, GMPCPP-stabilized MTs, serves as a model for the pause state of MT ends and that the multiple activities of XMAP215 are unified by a mechanism of antagonizing MT pauses.

PubMed ID: 12719474
PMC ID: PMC2172913
Article link: J Cell Biol
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: ckap5 kif2c rbl2 stmn1 tbx2

Article Images: [+] show captions
References [+] :
Belmont, Identification of a protein that interacts with tubulin dimers and increases the catastrophe rate of microtubules. 1996, Pubmed, Xenbase