Borisy G G, Taylor E W
J Cell Biol. 1967 Aug;34(2):525-33. doi: 10.1083/jcb.34.2.525.
The majority of the colchicine-(3)H bound by tissue culture cells (KB or Hela) was found to be present as a noncovalent complex with a macromolecule which appears in the soluble fraction after homogenization. Similar binding was demonstrated in vitro and was confined to a component of the soluble fraction. The binding-equilibrium constant and the kinetic constants were essentially the same in vivo and in vitro. Bound radioactivity was reisolated and shown to be present in a molecule with the same chromatographic behavior and specific antimitotic activity as colchicine. In vitro assay of binding activity of a variety of cells and tissues showed a correlation with the presence of microtubules. High binding activity was given by dividing cells, mitotic apparatus, cilia, sperm tails, and brain tissue. Binding to extracts of slime mold or to purified muscle proteins was very low or undetectable. The binding site had a sedimentation constant of 6S and it is suggested that the protein is a subunit of microtubules.
研究发现，组织培养细胞（KB或Hela）结合的大部分秋水仙碱 -（3）H以与一种大分子的非共价复合物形式存在，该大分子在匀浆后出现在可溶部分。体外实验也证实了类似的结合，且这种结合局限于可溶部分的一个组分。体内和体外的结合平衡常数及动力学常数基本相同。结合的放射性物质被重新分离出来，结果表明它存在于一种分子中，该分子具有与秋水仙碱相同的色谱行为和特定抗有丝分裂活性。对多种细胞和组织的结合活性进行体外测定，结果显示其与微管的存在相关。正在分裂的细胞、有丝分裂器、纤毛、精子尾部和脑组织具有较高的结合活性。与黏菌提取物或纯化的肌肉蛋白的结合非常低或无法检测到。结合位点的沉降常数为6S，推测该蛋白质是微管的一个亚基。
