King S M, Barbarese E, Dillman J F, Benashski S E, Do K T, Patel-King R S, Pfister K K
Department of Biochemistry, Center for Biomedical Imaging Technology, University of Connecticut Health Center, Farmington 06032-3305, USA.
Biochemistry. 1998 Oct 27;37(43):15033-41. doi: 10.1021/bi9810813.
Cytoplasmic dynein contains a series of accessory proteins associated with the motor containing heavy chains.1 These include three distinct classes of light chains (Mr < approximately 22 000). Here we demonstrate that a previously cloned protein termed rp3 is a bona fide Mr 14 000 light chain component of this microtubule motor complex. The rp3 polypeptide is approximately 55% identical to the Tctex1 dynein light chain, and together, these two proteins define one branch of a diverse family of Mr 14 000 light chains associated with both cytoplasmic and flagellar dyneins. The Tctex1 and rp3 light chains are differentially expressed in various tissues: rp3 is most prevalent in liver and brain cytoplasmic dynein, whereas those tissues contain the least amounts of Tctex1. Immunofluorescence analysis was consistent with the tissue-specific distribution of these proteins and revealed that both rp3 and Tctex1 are present in multiple perinuclear punctate particles. Furthermore, in two cell lines, rp3 was found associated with an elongated structure located in the layer of cytoplasm above the nucleus. Electrophoretic/immunological analysis indicates that there are only single isoforms for these proteins in brain and PC-12 cells, suggesting that alterations in the Mr 14 000 light chains of dynein are achieved at the level of the individual proteins and not by posttranslational modification. Dissection of the cytoplasmic dynein complex revealed that Tctex1, an Mr 8000 LC dimer, and IC74 associate to define a basal-located intermediate chain/light chain complex analogous to that found in flagellar outer arm dynein.
胞质动力蛋白包含一系列与含有重链的马达蛋白相关的辅助蛋白。这些蛋白包括三类不同的轻链（分子量<约22000）。在此，我们证明一种先前克隆的名为rp3的蛋白是这种微管马达复合体真正的分子量为14000的轻链成分。rp3多肽与Tctex1动力蛋白轻链约55%相同，并且这两种蛋白共同定义了与胞质和鞭毛动力蛋白相关的分子量为14000的轻链多样家族中的一个分支。Tctex1和rp3轻链在不同组织中差异表达：rp3在肝脏和脑胞质动力蛋白中最为普遍，而那些组织中Tctex1的含量最少。免疫荧光分析与这些蛋白的组织特异性分布一致，并显示rp3和Tctex1都存在于多个核周点状颗粒中。此外，在两种细胞系中，发现rp3与位于细胞核上方细胞质层中的一种细长结构相关。电泳/免疫分析表明，在脑和PC - 12细胞中这些蛋白只有单一异构体，这表明动力蛋白分子量为14000的轻链的改变是在单个蛋白水平上实现的，而不是通过翻译后修饰。对胞质动力蛋白复合体的剖析表明，Tctex1，一种分子量为8000的轻链二聚体，与IC74结合，定义了一种位于基部的中间链/轻链复合体，类似于在鞭毛外臂动力蛋白中发现的复合体。
