Honts J E, Williams N E
Department of Biology, University of Iowa, Iowa City 52242.
J Cell Sci. 1990 Jun;96 ( Pt 2):293-302. doi: 10.1242/jcs.96.2.293.
The cortex of the ciliated protozoan Tetrahymena contains a number of fibrous elements, including a network of filaments that pervades the feeding organelle of this organism. The cluster of polypeptides (79-89K; K = 10(3) Mr) in Tetrahymena pyriformis GL-C that constitute these filaments has been purified by in vitro assembly after solubilization in 1.0 M KI. Four distinct sets of these polypeptides, designated 'tetrins', have been shown to be distinguishable from each other by immunochemical and biochemical criteria. The smallest filaments reassembled in vitro were 3-4 nm in diameter and these fine filaments were seen to be bundled together into thicker strands of varying diameters, similar to those within the cell. The thicker filament bundles were clearly distinguishable from intermediate filaments, but fine filaments in these bundles were superficially similar to the 2-5 nm filaments described as microtubule-associated proteins in other organisms. The ultrastructure of the tetrin filaments localized within the feeding organelle reveals a substantial presence of these filaments apart from microtubules. In addition, circular dichroism measurements indicate a relatively low alpha-helical content for these filaments and suggest that the tetrins may be substantially different from other fine filament proteins such as the tektins and giardins.
纤毛原生动物四膜虫的皮层含有许多纤维成分，包括遍布该生物体摄食细胞器的丝状网络。梨形四膜虫GL-C中构成这些细丝的多肽簇（79 - 89K；K = 10³ 分子量）在1.0 M KI中溶解后通过体外组装进行了纯化。这些多肽有四组不同的类型，称为“四膜蛋白”，已通过免疫化学和生化标准证明它们彼此可区分。体外重新组装的最小细丝直径为3 - 4纳米，这些细丝被观察到聚集在一起形成不同直径的较粗股线，类似于细胞内的那些。较粗的细丝束与中间丝明显不同，但这些束中的细丝在表面上类似于在其他生物体中被描述为微管相关蛋白的2 - 5纳米细丝。位于摄食细胞器内的四膜蛋白细丝的超微结构显示，除了微管外，这些细丝大量存在。此外，圆二色性测量表明这些细丝的α - 螺旋含量相对较低，并表明四膜蛋白可能与其他细丝蛋白如轴丝蛋白和贾第虫蛋白有很大不同。
