DiBella Linda M, Smith Elizabeth F, Patel-King Ramila S, Wakabayashi Ken-ichi, King Stephen M
Department of Biochemistry, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3305, USA.
J Biol Chem. 2004 May 14;279(20):21666-76. doi: 10.1074/jbc.M313540200. Epub 2004 Mar 11.
Tctex1 and Tctex2 were originally described in mice as putative distorters/sterility factors involved in the non-Mendelian transmission of t haplotypes. Subsequently, these proteins were found to be light chains of both cytoplasmic and axonemal dyneins. We have now identified a novel Tctex2-related protein (Tctex2b) within the Chlamydomonas flagellum. Tctex2b copurifies with inner arm I1 after both sucrose gradient centrifugation and anion exchange chromatography. Unlike the Tctex2 homologue within the outer dynein arm, analysis of a Tctex2b-null strain indicates that this protein is not essential for assembly of inner arm I1. However, a lack of Tctex2b results in an unstable dynein particle that disassembles after high salt extraction from the axoneme. Cells lacking Tctex2b swim more slowly than wild type and exhibit a reduced flagellar beat frequency. Furthermore, using a microtubule sliding assay we observed that dynein motor function is reduced in vitro. These data indicate that Tctex2b is required for the stability of inner dynein arm I1 and wild-type axonemal dynein function.
Tctex1和Tctex2最初在小鼠中被描述为与t单倍型的非孟德尔遗传相关的假定畸变/不育因子。随后，发现这些蛋白质是细胞质和轴丝动力蛋白的轻链。我们现在在衣藻鞭毛中鉴定出一种新的Tctex2相关蛋白（Tctex2b）。在蔗糖梯度离心和阴离子交换色谱后，Tctex2b与内臂I1共纯化。与外动力蛋白臂中的Tctex2同源物不同，对Tctex2b缺失菌株的分析表明，该蛋白对于内臂I1的组装不是必需的。然而，缺乏Tctex2b会导致动力蛋白颗粒不稳定，在从轴丝中进行高盐提取后会解体。缺乏Tctex2b的细胞比野生型游动得更慢，并且鞭毛搏动频率降低。此外，使用微管滑动试验，我们观察到体外动力蛋白运动功能降低。这些数据表明，Tctex2b是内动力蛋白臂I1的稳定性和野生型轴丝动力蛋白功能所必需的。
