Edwards Marc, McConnell Patrick, Schafer Dorothy A, Cooper John A
Department of Cell Biology and Physiology, Washington University School of Medicine, St Louis, Missouri 63110-1093, USA.
Departments of Biology and Cell Biology, University of Virginia, Charlottesville, Virginia 22904-4328, USA.
Nat Commun. 2015 Sep 28;6:8415. doi: 10.1038/ncomms9415.
Capping protein (CP) has critical roles in actin assembly in vivo and in vitro. CP binds with high affinity to the barbed end of actin filaments, blocking the addition and loss of actin subunits. Heretofore, models for actin assembly in cells generally assumed that CP is constitutively active, diffusing freely to find and cap barbed ends. However, CP can be regulated by binding of the 'capping protein interaction' (CPI) motif, found in a diverse and otherwise unrelated set of proteins that decreases, but does not abolish, the actin-capping activity of CP and promotes uncapping in biochemical experiments. Here, we report that CP localization and the ability of CP to function in cells requires interaction with a CPI-motif-containing protein. Our discovery shows that cells target and/or modulate the capping activity of CP via CPI motif interactions in order for CP to localize and function in cells.
封端蛋白（CP）在体内和体外的肌动蛋白组装过程中发挥着关键作用。CP以高亲和力与肌动蛋白丝的带刺末端结合，阻止肌动蛋白亚基的添加和丢失。迄今为止，细胞中肌动蛋白组装的模型通常假定CP具有组成性活性，可自由扩散以找到并封端带刺末端。然而，CP可通过与“封端蛋白相互作用”（CPI）基序结合来进行调节，该基序存在于一组多样且无其他关联的蛋白质中，在生化实验中，它会降低但不会消除CP的肌动蛋白封端活性，并促进解封端。在此，我们报告CP在细胞中的定位以及CP在细胞中发挥功能的能力需要与含有CPI基序的蛋白质相互作用。我们的发现表明，细胞通过CPI基序相互作用来靶向和/或调节CP的封端活性，以使CP在细胞中定位并发挥功能。
