Wang Y X, Catlett N L, Weisman L S
Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA.
J Cell Biol. 1998 Mar 9;140(5):1063-74. doi: 10.1083/jcb.140.5.1063.
During each cell cycle, the yeast vacuole actively partitions between mother and daughter cells. This process requires actin, profilin, an unconventional myosin (Myo2p), and Vac8p. A mutant yeast strain, vac8, is defective in vacuole inheritance, specifically, in early vacuole migration. Vac8p is a 64-kD protein found on the vacuole membrane, a site consistent with its role in vacuole inheritance. Both myristoylation and palmitoylation are required for complete Vac8p localization. Interestingly, whereas myristoylation of Vac8p is not required for vacuole inheritance, palmitoylation is essential. Thus, palmitoylation appears to play a more direct role in vacuole inheritance. Most of the VAC8 sequence encodes 11 armadillo (Arm) repeats. Arm repeats are thought to mediate protein-protein interactions, and many Arm proteins have multiple functions. This is also true for Vac8p. In addition to its role in early vacuole inheritance, Vac8p is required to target aminopeptidase I from the cytoplasm to the vacuole. Mutant analysis demonstrates that Vac8p functions separately in these two processes. Vac8p cosediments with actin filaments. Vac8p is related to beta-catenin and plakoglobin, which connect a specific region of the plasma membrane to the actin cytoskeleton. In analogy, Vac8p may link the vacuole to actin during vacuole partitioning.
在每个细胞周期中，酵母液泡会在母细胞和子细胞之间进行活跃的分配。这个过程需要肌动蛋白、肌动蛋白结合蛋白、一种非常规肌球蛋白（Myo2p）和Vac8p。一种突变酵母菌株vac8在液泡遗传方面存在缺陷，具体表现为早期液泡迁移缺陷。Vac8p是一种在液泡膜上发现的64-kD蛋白，这一位置与其在液泡遗传中的作用相符。完全的Vac8p定位需要肉豆蔻酰化和棕榈酰化。有趣的是，虽然Vac8p的肉豆蔻酰化对于液泡遗传不是必需的，但棕榈酰化却是至关重要的。因此，棕榈酰化似乎在液泡遗传中发挥着更直接的作用。VAC8序列的大部分编码11个犰狳（Arm）重复序列。Arm重复序列被认为可介导蛋白质-蛋白质相互作用，许多含Arm的蛋白质具有多种功能。Vac8p也是如此。除了在早期液泡遗传中的作用外，Vac8p还需要将细胞质中的氨肽酶I靶向运输到液泡。突变分析表明Vac8p在这两个过程中分别发挥作用。Vac8p与肌动蛋白丝共沉降。Vac8p与β-连环蛋白和桥粒芯蛋白相关，它们将质膜的特定区域与肌动蛋白细胞骨架相连。类似地，Vac8p可能在液泡分配过程中将液泡与肌动蛋白相连。
