Joly J C, Flynn G, Purich D L
Department of Biochemistry and Molecular Biology, University of Florida College of Medicine, Gainesville 32610.
J Cell Biol. 1989 Nov;109(5):2289-94. doi: 10.1083/jcb.109.5.2289.
Thrombin cleavage of bovine brain microtubule-associated protein (MAP-2) yields two stable limit polypeptide fragments (28,000 and 240,000 Mr). The smaller cleavage product contains the microtubule-binding domain and is derived from the carboxyl terminus of MAP-2 while the 240,000 Mr fragment is derived from the amino terminus. The amino terminal sequence of the smaller cleavage product is homologous with the microtubule-binding fragment of tau in sequence and in a similar location relative to three imperfect octadecapeptide repeats implicated in microtubule binding. Peptides corresponding to the cleavage site and the three repeats of MAP-2 were synthesized. Only the second octadecapeptide repeat (VTSKCGSLKNIRHRPGGG) was capable of stimulating microtubule nucleation and elongation. Microtubules formed in the presence of this peptide displayed normal morphology and retained the inhibition properties of calcium ion, podophyllotoxin, and colchicine. Our result indicates that a region comprising only approximately 1% of the MAP-2 sequence can promote microtubule assembly.
凝血酶对牛脑微管相关蛋白（MAP - 2）进行切割会产生两个稳定的极限多肽片段（分子量分别为28,000和240,000）。较小的切割产物包含微管结合结构域，它源自MAP - 2的羧基末端，而240,000分子量的片段源自氨基末端。较小切割产物的氨基末端序列在序列上与tau蛋白的微管结合片段同源，并且相对于与微管结合相关的三个不完全的十八肽重复序列，其位置相似。合成了与MAP - 2的切割位点及三个重复序列相对应的肽段。只有第二个十八肽重复序列（VTSKCGSLKNIRHRPGGG）能够刺激微管的成核和延长。在该肽段存在的情况下形成的微管呈现正常形态，并保留了对钙离子、鬼臼毒素和秋水仙碱的抑制特性。我们的结果表明，仅占MAP - 2序列约1%的一个区域就能促进微管组装。
