Amatruda J F, Cooper J A
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri 63110.
J Cell Biol. 1992 Jun;117(5):1067-76. doi: 10.1083/jcb.117.5.1067.
Capping protein binds the barbed ends of actin filaments and nucleates actin filament assembly in vitro. We purified capping protein from Saccharomyces cervisiae. One of the two subunits is the product of the CAP2 gene, which we previously identified as the gene encoding the beta subunit of capping protein based on its sequence similarity to capping protein beta subunits in chicken and Dictyostelium (Amatruda, J. F., J. F. Cannon, K. Tatchell, C. Hug, and J. A. Cooper. 1990. Nature (Lond.) 344:352-354). Yeast capping protein has activity in critical concentration and low-shear viscometry assays consistent with barbed-end capping activity. Like chicken capping protein, yeast capping protein is inhibited by PIP2. By immunofluorescence microscopy yeast capping protein colocalizes with cortical actin spots at the site of bud emergence and at the tips of growing buds and shmoos. In contrast, capping protein does not colocalize with actin cables or with actin rings at the site of cytokinesis.
封端蛋白可结合肌动蛋白丝的尖端，并在体外促使肌动蛋白丝组装成核。我们从酿酒酵母中纯化了封端蛋白。两个亚基之一是CAP2基因的产物，基于其与鸡和盘基网柄菌中封端蛋白β亚基的序列相似性，我们之前已将该基因鉴定为编码封端蛋白β亚基的基因（阿马特拉达，J.F.，J.F.坎农，K.塔切尔，C.胡格，和J.A.库珀。1990年。《自然》（伦敦）344:352 - 354）。酵母封端蛋白在临界浓度和低剪切粘度测定中表现出与尖端封端活性一致的活性。与鸡封端蛋白一样，酵母封端蛋白受到磷脂酰肌醇 - 4,5 - 二磷酸（PIP2）的抑制。通过免疫荧光显微镜观察，酵母封端蛋白在芽出现的部位以及生长中的芽和芽殖体的尖端与皮质肌动蛋白斑点共定位。相比之下，封端蛋白在胞质分裂部位不与肌动蛋白索或肌动蛋白环共定位。
