Johnston G C, Prendergast J A, Singer R A
Department of Microbiology, Dalhousie University, Halifax, Nova Scotia, Canada.
J Cell Biol. 1991 May;113(3):539-51. doi: 10.1083/jcb.113.3.539.
After the initiation of bud formation, cells of the yeast Saccharomyces cerevisiae direct new growth to the developing bud. We show here that this vectorial growth is facilitated by activity of the MYO2 gene. The wild-type MYO2 gene encodes an essential form of myosin composed of an NH2-terminal domain typical of the globular, actin-binding domain of other myosins. This NH2-terminal domain is linked by what appears to be a short alpha-helical domain to a novel COOH-terminal region. At the restrictive temperature the myo2-66 mutation does not impair DNA, RNA, or protein biosynthetic activity, but produces unbudded, enlarged cells. This phenotype suggests a defect in localization of cell growth. Measurements of cell size demonstrated that the continued development of initiated buds, as well as bud initiation itself, is inhibited. Bulk secretion continues in mutant cells, although secretory vesicles accumulate. The MYO2 myosin thus may function as the molecular motor to transport secretory vesicles along actin cables to the site of bud development.
在酵母酿酒酵母开始形成芽之后，其细胞将新的生长导向正在发育的芽。我们在此表明，这种定向生长是由MYO2基因的活性促进的。野生型MYO2基因编码一种肌球蛋白的必需形式，该肌球蛋白由一个NH2末端结构域组成，该结构域是其他肌球蛋白的球状肌动蛋白结合结构域所特有的。这个NH2末端结构域通过一个似乎是短α螺旋结构域与一个新的COOH末端区域相连。在限制温度下，myo2-66突变不会损害DNA、RNA或蛋白质的生物合成活性，但会产生未出芽的、增大的细胞。这种表型表明细胞生长定位存在缺陷。细胞大小的测量表明，已起始芽的持续发育以及芽的起始本身均受到抑制。尽管分泌小泡会积累，但突变细胞中的大量分泌仍在继续。因此，MYO2肌球蛋白可能作为分子马达，沿着肌动蛋白丝将分泌小泡运输到芽发育的部位。
