EFFECT ON MICROTUBULE DYNAMICS OF XMAP230, A MICROTUBULE-ASSOCIATED PROTEIN PRESENT IN XENOPUS-LAEVIS EGGS AND DIVIDING CELLS
EFFECT ON MICROTUBULE DYNAMICS OF XMAP230, A MICROTUBULE-ASSOCIATED PROTEIN PRESENT IN XENOPUS-LAEVIS EGGS AND DIVIDING CELLS
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DOI：
10.1083/jcb.127.5.1289
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发表时间：
1994-12-01
影响因子：
7.8
通讯作者：
KARSENTI, E
中科院分区：
文献类型：
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作者：
ANDERSEN, SSL;BUENDIA, B;KARSENTI, E
在有丝分裂开始时，从自由基间期微管（MT）网络重组为双极纺锤体涉及MT动力学的巨大变化。微管相关蛋白（MAPs）和其他因子被认为在间期和有丝分裂中调节MT动力学。在这项研究中，我们报告了从非洲爪蟾卵提取物（XMAP 230）的230-KD MAP的纯化和功能在体外表征。这种蛋白存在于卵、卵母细胞、睾丸和非洲爪蟾组织培养细胞系中。它显然是缺乏非分裂细胞中发现一个免疫相关的200 kD蛋白。XMAP 230是由两个异构体略有不同的分子量和pI。它定位于间期MT，在前期开始时与MT解离，并在中期和后期特异性结合纺锤体MT。XMAP 230的解离常数为500 nM，与MT结合的化学计量在1：8和1：4之间，体内浓度与200 nM相似。这两种亚型都被磷酸化，并且在有丝分裂提取物中对微管的亲和力降低。通过视频显微镜分析XMAP 230对MT动力学的影响表明，它增加了MT的生长速率，降低了MT的收缩速率，并强烈抑制了突变。这些结果表明，在体内，XMAP 230参与控制的MT延长率，稳定MT和局部调节MT动力学在有丝分裂。
The reorganization from a radical interphase microtubule (MT) network into a bipolar spindle at the onset of mitosis involves a dramatic change in MT dynamics. Microtubule-associated proteins (MAPs) and other factors are thought to regulate MT dynamics both in interphase and in mitosis. In this study we report the purification and functional in vitro characterization of a 230-KD MAP from Xenopus egg extract (XMAP230). This protein is present in eggs, oocytes, testis and a Xenopus tissue culture cell line. It is apparently absent from non-dividing cells in which an immunologically related 200-kD protein is found. XMAP230 is composed of two isoforms with slightly different molecular masses and pIs. It is localized to interphase MTs, dissociates from MTs at the onset of prophase and specifically binds to spindle MTs during metaphase and anaphase. The dissociation constant of XMAP230 is 500 nM, the stoichiometry of binding to MTs is between 1:8 and 1:4, and the in vivo concentration is similar to 200 nM. Both isoforms are phosphorylated and have reduced affinity for microtubules in mitotic extracts. Analysis of the effect of XMAP230 on MT dynamics by video microscopy shows that it increases the growth rate, decreases the shrinking rate of MTs and strongly suppresses catastrophes. These results suggest that in vivo, XMAP230 participates in the control of the MT elongation rate, stabilizes MTs and locally modulates MT dynamics during mitosis.