Stephens R E
J Cell Biol. 1982 Aug;94(2):263-70. doi: 10.1083/jcb.94.2.263.
Two equimolar beta chains can be resolved from sea urchin sperm flagellar and scallop gill ciliary tubulins, and from certain brain tubulins as well, using the Triton X-100-acid-urea polyacrylamide gel system commonly used for histone analysis. The beta chains are identified as such from their mobility on urea-free SDS PAGE, from amino acid composition, and from tryptic peptide distribution. Scallop beta chains have almost identical amino acid profiles but they differ by one tryptic peptide. Optimal conditions for beta chain resolution are very species-dependent, with some closely related species showing either maximal or no beta chain separation. In addition, beef brain tubulin on Triton X-100-acid-urea electrophoresis and scallop gill ciliary tubulin upon isoelectric focusing in the presence of SDS show two approximately equimolar alpha chains. These data, indicating equimolar amounts of two potentially different tubulin heterodimers from a variety of microtubule types, support a model for microtubule structure wherein protofilaments consist of alternating heterodimers of two kinds, generating a 16-nm (2-dimer) axial repeat.
使用常用于组蛋白分析的Triton X-100-酸-尿素聚丙烯酰胺凝胶系统,可以从海胆精子鞭毛、扇贝鳃纤毛微管蛋白以及某些脑微管蛋白中分离出两条等摩尔的β链。通过它们在无尿素SDS-PAGE上的迁移率、氨基酸组成和胰蛋白酶肽分布来鉴定β链。扇贝的β链具有几乎相同的氨基酸谱,但它们在一个胰蛋白酶肽上有所不同。β链分离的最佳条件非常依赖物种,一些密切相关的物种显示出最大程度的β链分离或根本没有β链分离。此外,牛肉脑微管蛋白在Triton X-100-酸-尿素电泳上以及扇贝鳃纤毛微管蛋白在SDS存在下的等电聚焦显示出两条近似等摩尔的α链。这些数据表明,来自各种微管类型的两种潜在不同的微管蛋白异二聚体的量是等摩尔的,支持了一种微管结构模型,其中原纤维由两种交替的异二聚体组成,并产生16纳米(2个二聚体)的轴向重复。