期刊
JOURNAL OF CELL BIOLOGY
卷 161, 期 2, 页码 349-358出版社
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.200211095
关键词
microtubule dynamics; microtubule-associated protein; XMAP215; GMPCPP; depolymerization
类别
资金
- NIGMS NIH HHS [R37 GM039565, R01 GM039565, GM39565] Funding Source: Medline
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/Kinl). 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.
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