Culver-Hanlon Tara L, Lex Stephanie A, Stephens Andrew D, Quintyne Nicholas J, King Stephen J
Division of Molecular Biology and Biochemistry, School of Biological Sciences, University of Missouri-Kansas City, 5007 Rockhill Rd., Kansas City, MO 64110, USA.
Nat Cell Biol. 2006 Mar;8(3):264-70. doi: 10.1038/ncb1370. Epub 2006 Feb 12.
Microtubule-associated proteins (MAPs) use particular microtubule-binding domains that allow them to interact with microtubules in a manner specific to their individual cellular functions. Here, we have identified a highly basic microtubule-binding domain in the p150 subunit of dynactin that is only present in the dynactin members of the CAP-Gly family of proteins. Using single-particle microtubule-binding assays, we found that the basic domain of dynactin moves progressively along microtubules in the absence of molecular motors - a process we term 'skating'. In contrast, the previously described CAP-Gly domain of dynactin remains firmly attached to a single point on microtubules. Further analyses showed that microtubule skating is a form of one-dimensional diffusion along the microtubule. To determine the cellular function of the skating phenomenon, dynein and the dynactin microtubule-binding domains were examined in single-molecule motility assays. We found that the basic domain increased dynein processivity fourfold whereas the CAP-Gly domain inhibited dynein motility. Our data show that the ability of the basic domain of dynactin to skate along microtubules is used by dynein to maintain longer interactions for each encounter with microtubules.
微管相关蛋白（MAPs）利用特定的微管结合结构域，使其能够以与其各自细胞功能特异的方式与微管相互作用。在此，我们在动力蛋白激活蛋白的p150亚基中鉴定出一个高度碱性的微管结合结构域，该结构域仅存在于CAP-Gly蛋白家族的动力蛋白激活蛋白成员中。通过单颗粒微管结合试验，我们发现动力蛋白激活蛋白的碱性结构域在没有分子马达的情况下沿微管逐渐移动——我们将这一过程称为“滑行”。相比之下，先前描述的动力蛋白激活蛋白的CAP-Gly结构域则牢固地附着在微管上的单个点上。进一步分析表明，微管滑行是沿微管的一维扩散形式。为了确定滑行现象的细胞功能，我们在单分子运动试验中检测了动力蛋白和动力蛋白激活蛋白的微管结合结构域。我们发现碱性结构域使动力蛋白的持续运动能力提高了四倍，而CAP-Gly结构域则抑制了动力蛋白的运动。我们的数据表明，动力蛋白激活蛋白的碱性结构域沿微管滑行的能力被动力蛋白用来在每次与微管相遇时维持更长时间的相互作用。
