Liu Zhongmei, Takazaki Hiroko, Nakazawa Yuki, Sakato Miho, Yagi Toshiki, Yasunaga Takuo, King Stephen M, Kamiya Ritsu
Department of Biological Sciences, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
Eukaryot Cell. 2008 Jul;7(7):1136-45. doi: 10.1128/EC.00102-08. Epub 2008 May 16.
The outer dynein arm of Chlamydomonas flagella contains three heavy chains (alpha, beta, and gamma), each of which exhibits motor activity. How they assemble and cooperate is of considerable interest. Here we report the isolation of a novel mutant, oda2-t, whose gamma heavy chain is truncated at about 30% of the sequence. While the previously isolated gamma chain mutant oda2 lacks the entire outer arm, oda2-t retains outer arms that contain alpha and beta heavy chains, suggesting that the N-terminal sequence (corresponding to the tail region) is necessary and sufficient for stable outer-arm assembly. Thin-section electron microscopy and image analysis localize the gamma heavy chain to a basal region of the outer-arm image in the axonemal cross section. The motility of oda2-t is lower than that of the wild type and oda11 (lacking the alpha heavy chain) but higher than that of oda2 and oda4-s7 (lacking the motor domain of the beta heavy chain). Thus, the outer-arm dynein lacking the gamma heavy-chain motor domain is partially functional. The availability of mutants lacking individual heavy chains should greatly facilitate studies on the structure and function of the outer-arm dynein.
衣藻鞭毛的外动力蛋白臂包含三条重链（α、β和γ），每条重链都具有运动活性。它们如何组装和协作备受关注。在此，我们报告了一种新型突变体oda2-t的分离，其γ重链在大约30%的序列处被截断。虽然之前分离的γ链突变体oda2缺乏整个外臂，但oda2-t保留了包含α和β重链的外臂，这表明N端序列（对应于尾部区域）对于稳定的外臂组装是必要且充分的。超薄切片电子显微镜和图像分析将γ重链定位到轴丝横切面中外臂图像的基部区域。oda2-t的运动能力低于野生型和oda11（缺乏α重链），但高于oda2和oda4-s7（缺乏β重链的运动结构域）。因此，缺乏γ重链运动结构域的外臂动力蛋白部分具有功能。缺乏单个重链的突变体的可得性将极大地促进对外臂动力蛋白结构和功能的研究。
