Vallee R B, Borisy G G
J Biol Chem. 1978 Apr 25;253(8):2834-45.
We have investigated the association of non-tubulin microtubule proteins with tubulin to form the ring-shaped oligomeric structures found in microtubule preparations. We have found that the two oligomeric species present in our preparations of microtubule protein (s020,w = 18 and 30 S) each require non-tubulin factors for their formation. Two types of non-tubulin protein, the high molecular weight proteins (HMW) and the tau proteins were found to be active in ring formation. The HMW proteins promoted the formation of the 30 S oligomer, while the tau proteins promoted the formation of an oligomer of s020,w = 20 S. Analysis of the 30 S oligomer by gel filtration chromatography showed that the ratio of HMW proteins to tubulin was about twice that in the microtubule. The HMW proteins could be destroyed by exposure to trypsin, resulting in a marked increase in the sedimentation coefficient of the 30 S oligomer to 39 S. The 20, 30, and 39 S species were identified as rings by electron microscopy. The identity of the 18 S structure as a ring was called into question. Our data indicate that the 20 S species is a single ring and that the 30 S oligomer is a two-layered ring bearing HMW projections which contribute substantial hydrodynamic drag to the particle. We compare the organization of tubulin subunits and HMW molecules in the 30 S ring with the organization of these components in the microtubule and suggest that the organization in the ring is conserved in the microtubule.
我们研究了非微管蛋白微管蛋白与微管蛋白形成微管制剂中发现的环状寡聚结构的关联。我们发现，微管蛋白制剂（s020，w = 18和30 S）中存在的两种寡聚体各自形成均需要非微管蛋白因子。发现两种类型的非微管蛋白，即高分子量蛋白（HMW）和tau蛋白在环形成中具有活性。HMW蛋白促进30 S寡聚体的形成，而tau蛋白促进s020，w = 20 S寡聚体的形成。通过凝胶过滤色谱法对30 S寡聚体进行分析表明，HMW蛋白与微管蛋白的比例约为微管中的两倍。暴露于胰蛋白酶可破坏HMW蛋白，导致30 S寡聚体的沉降系数显著增加至39 S。通过电子显微镜鉴定20、30和39 S物种为环。18 S结构是否为环受到质疑。我们的数据表明，20 S物种是单环，30 S寡聚体是带有HMW突起的双层环，这些突起对颗粒产生了显著的流体动力学阻力。我们将30 S环中微管蛋白亚基和HMW分子的组织与微管中这些成分的组织进行比较，并表明环中的组织在微管中是保守的。
