Vallee R B
J Cell Biol. 1982 Feb;92(2):435-42. doi: 10.1083/jcb.92.2.435.
The effect of the antimitotic drug taxol on the association of MAPs (microtubule-associated proteins) with microtubules was investigated. Extensive microtubule assembly occurred in the presence of Taxol at 37 degrees C. at 0 degrees C, and at 37 degrees C in the presence of 0.35 M NaCl, overcoming the inhibition of assembly normally observed under the latter two conditions. At 37 degrees C and at 0 degrees C, complete assembly of both tubulin and the MAPs was observed in the presence of Taxol. However, at elevated ionic strength, only tubulin assembled, forming microtubules devoid of MAPs. The MAPs could also be released from the surface of preformed microtubules by exposure to elevated ionic strength. These properties provided the basis for a rapid new procedure for isolating microtubules and MAPs of high purity from small amounts of biological material. The MAPs could be recovered by exposure of the microtubules to elevated ionic strength and subjected to further analysis. Microtubules and MAPs were prepared from bovine cerebral cortex (gray matter) and from HeLa cells. MAP 1, MAP2, and the tau MAPs, as well as species of Mr = 28,000 and 30,000 (LMW, or low molecular weight, MAPs) and a species of Mr = 70,000 were isolated from gray matter. Species identified as the 210,000 and 125,000 mol wt HeLa MAPs were isolated from HeLa cells. Microtubules were also prepared for the first time from white matter. All of the MAPs identified in gray matter preparations were identified in white matter, but the amounts of individual MAP species differed. The most striking difference in the two preparations was a fivefold lower level of MAP 2 relative to tubulin in white matter than in gray. The high molecular weigh MAP, MAP1, was present in equal ratio to tubulin in white and gray matter. These results indicate that MAP 1 and MAP2, as well as other MAP species, may have a different cellular or subcellular distribution.
研究了抗有丝分裂药物紫杉醇对微管相关蛋白（MAPs）与微管结合的影响。在37℃、0℃以及37℃且存在0.35M氯化钠的条件下，紫杉醇存在时会发生广泛的微管组装，克服了在后两种条件下通常观察到的组装抑制。在37℃和0℃时，在紫杉醇存在下观察到微管蛋白和MAPs均完全组装。然而，在离子强度升高时，只有微管蛋白组装，形成不含MAPs的微管。通过暴露于升高的离子强度，MAPs也可从预先形成的微管表面释放。这些特性为从少量生物材料中快速分离高纯度微管和MAPs的新方法提供了基础。通过将微管暴露于升高的离子强度可回收MAPs，并进行进一步分析。微管和MAPs取自牛脑皮层（灰质）和HeLa细胞。从灰质中分离出了MAP1、MAP2和tau MAPs，以及分子量为28,000和30,000的物种（低分子量MAPs）和一种分子量为70,000的物种。从HeLa细胞中分离出了鉴定为分子量210,000和125,000的HeLa MAPs物种。还首次从白质中制备了微管。在灰质制剂中鉴定出的所有MAPs在白质中也都有，但各个MAP物种的含量不同。两种制剂中最显著的差异是，相对于微管蛋白，白质中MAP2的水平比灰质中低五倍。高分子量MAP，即MAP1，在白质和灰质中与微管蛋白的比例相同。这些结果表明，MAP1和MAP2以及其他MAP物种可能具有不同的细胞或亚细胞分布。
