Takeuchi M, Hisanaga S, Umeyama T, Hirokawa N
Department of Anatomy and Cell Biology, Faculty of Medicine, University of Tokyo, Japan.
J Neurochem. 1992 Apr;58(4):1510-6. doi: 10.1111/j.1471-4159.1992.tb11372.x.
A microtubule-associated protein (MAP) with a molecular mass of 72-kDa that was purified from porcine brain by using its property of heat stability in a low pH buffer was characterized. Low-angle rotary shadowing revealed that the 72-kDa protein was a rodlike protein approximately 55-75 nm long. The 72-kDa protein bound to microtubules polymerized from phosphocellulose column-purified tubulin (PC-tubulin) with taxol and promoted the polymerization of PC-tubulin in the absence of taxol. Microtubules polymerized by the 72-kDa protein showed a tendency to form bundles of several microtubules. Quick-freeze, deep-etch electron microscopy revealed that the 72-kDa protein formed short crossbridges between microtubules. We performed peptide mapping to analyze the relationship of the 72-kDa protein to other heat-stable MAPs, and the results showed some resemblance of the 72-kDa protein to MAP2. Cross-reactivity with a monoclonal anti-MAP2 antibody further suggested that the 72-kDa protein and MAP2 are immunologically related. To study the relationship between the 72-kDa protein and MAP2C, a smaller molecular form of MAP2 identified in juvenile rat brain, we prepared the 72-kDa protein from rat brain by the same method as that used for porcine brain. The fact that the 72-kDa protein from juvenile rat brain was also stained with our monoclonal anti-MAP2 antibody also suggested that the 72-kDa protein is an MAP2C homologue of the porcine brain.
通过利用其在低pH缓冲液中的热稳定性，从猪脑中纯化出一种分子量为72 kDa的微管相关蛋白（MAP），并对其进行了表征。低角度旋转阴影显示，72 kDa蛋白是一种杆状蛋白，长度约为55 - 75 nm。该72 kDa蛋白与从磷酸纤维素柱纯化的微管蛋白（PC - 微管蛋白）在紫杉醇存在下聚合形成的微管结合，并在没有紫杉醇的情况下促进PC - 微管蛋白的聚合。由72 kDa蛋白聚合形成的微管有形成几根微管束的趋势。快速冷冻、深度蚀刻电子显微镜显示，72 kDa蛋白在微管之间形成短的交叉桥。我们进行了肽图谱分析以研究72 kDa蛋白与其他热稳定MAP之间的关系，结果表明72 kDa蛋白与MAP2有一些相似之处。与单克隆抗MAP2抗体的交叉反应进一步表明72 kDa蛋白和MAP2在免疫上相关。为了研究72 kDa蛋白与MAP2C（在幼年大鼠脑中鉴定出的一种分子量较小的MAP2形式）之间的关系，我们用与从猪脑制备72 kDa蛋白相同的方法从大鼠脑中制备了该蛋白。幼年大鼠脑来源的72 kDa蛋白也能用我们的单克隆抗MAP2抗体染色这一事实也表明72 kDa蛋白是猪脑的MAP2C同源物。
