Department of Life Science, Graduate School of Life Science, University of Hyogo, Harima Science Park City, Hyogo 678-1297, Japan.
Plant Physiol. 2009 Dec;151(4):1823-30. doi: 10.1104/pp.109.144303. Epub 2009 Oct 23.
Widely conserved among eukaryotes, the microtubule-associated protein 215 (MAP215) family enhances microtubule dynamic instability. The family member studied most extensively, Xenopus laevis XMAP215, has been reported to enhance both assembly and disassembly parameters, although the mechanism whereby one protein can exert these apparently contradictory effects has not been clarified. Here, we analyze the activity of a plant MAP215 homolog, tobacco (Nicotiana tabacum) MAP200 on microtubule behavior in vitro. We show that, like XMAP215, MAP200 promotes both assembly and disassembly parameters, including microtubule growth rate and catastrophe frequency. When MAP200 is added to tubulin and taxol, strikingly long-coiled structures form. When GDP partially replaces GTP, the increase of catastrophe frequency by MAP200 is strongly diminished, even though this replacement stimulates catastrophe in the absence of MAP200. This implies that MAP200 induces catastrophes by a specific, GTP-requiring pathway. We hypothesize that, in the presence of MAP200, a catastrophe-prone microtubule lattice forms occasionally when elongated but nonadjacent protofilaments make lateral contacts.
微管相关蛋白 215（MAP215）家族在真核生物中广泛保守，可增强微管动态不稳定性。研究最广泛的家族成员，非洲爪蟾 XMAP215，据报道可增强组装和拆卸参数，尽管一种蛋白质如何发挥这些明显矛盾的作用的机制尚未阐明。在这里，我们分析了植物 MAP215 同源物，烟草（Nicotiana tabacum）MAP200 对体外微管行为的活性。我们表明，与 XMAP215 一样，MAP200 可促进组装和拆卸参数，包括微管生长速度和崩溃频率。当 MAP200 被添加到微管蛋白和紫杉醇中时，会形成非常长的螺旋结构。当 GDP 部分取代 GTP 时，MAP200 引起的崩溃频率会大大降低，尽管这种取代在没有 MAP200 的情况下会刺激崩溃。这意味着 MAP200 通过特定的、需要 GTP 的途径诱导崩溃。我们假设，在 MAP200 的存在下，当伸长但不相邻的原丝形成侧向接触时，偶尔会形成一个容易崩溃的微管晶格。
