The 65-kDa carrot microtubule-associated protein forms regularly arranged filamentous cross-bridges between microtubules
The 65-kDa carrot microtubule-associated protein forms regularly arranged filamentous cross-bridges between microtubules
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DOI：
10.1073/pnas.96.26.14931
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发表时间：
1999-12-21
影响因子：
11.1
通讯作者：
Lloyd, CW
中科院分区：
文献类型：
--
作者：
Chan, J;Jensen, CG;Lloyd, CW
在植物中，皮层微管（MT）以特征性的平行组出现，通过细丝状跨桥维持最多一微管直径的间隔。然而，迄今为止纯化的植物微管相关蛋白 (MAP) 都无法解释细胞中观察到的 MT 之间的分离，我们之前从胡萝卜细胞骨架中分离出包含 120-和 65-kDa MAP 的 MAP 级分，现在通过蔗糖密度离心分离了 65-kDa 胡萝卜 MAP，MAP65 不会诱导微管蛋白聚合，但会在核苷酸不敏感的情况下诱导平行 MT 束的形成方式。猪MAP2抑制成束效应，但与MAP2不同，MAP65对热不稳定。在电子显微镜下，MAP65表现为丝状交叉桥，保持25-30 nm的微管间距，微密度计-计算机相关分析表明，交叉桥间隔规则，显示出规则的轴向间距，与13个原丝的对称螺旋超晶格兼容。 MT。因为 MAP65 在体外维持了在植物中观察到的 MT 间距，并且显示出装饰皮质 MT，因此提出 MAP 对于体内皮质阵列的组织很重要。
In plants, cortical microtubules (MTs) occur in characteristically parallel groups maintained up to one microtubule diameter apart by fine filamentous cross-bridges. However, none of the plant microtubule-associated proteins (MAPs) so far purified accounts for the observed separation between MTs in cells, We previously isolated from carrot cytoskeletons a MAP fraction including 120- and 65-kDa MAPs and have now separated the 65-kDa carrot MAP by sucrose density centrifugation, MAP65 does not induce tubulin polymerization but induces the formation of bundles of parallel MTs in a nucleotide-insensitive manner. The bundling effect is inhibited by porcine MAP2, but, unlike MAP2, MAP65 is heat-labile, In the electron microscope, MAP65 appears as filamentous crossbridges, maintaining an intermicrotubule spacing of 25-30 nm, Microdensitometer-computer correlation analysis reveals that the cross-bridges are regularly spaced, showing a regular axial spacing that is compatible with a symmetrical helical superlattice for 13 protofilament MTs. Because MAP65 maintains in vitro the inter-MT spacing observed in plants and is shown to decorate cortical MTs, it is proposed that th is MAP is important for the organization of the cortical array in vivo.