Ichetovkin I, Han J, Pang K M, Knecht D A, Condeelis J S
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York, USA.
Cell Motil Cytoskeleton. 2000 Apr;45(4):293-306. doi: 10.1002/(SICI)1097-0169(200004)45:4<293::AID-CM5>3.0.CO;2-1.
Cofilin has been reported to depolymerize F-actin alternately by either severing filaments to increase the number of depolymerizing ends or by increasing the off-rate of monomers from F-actin without increasing the number of filament ends. We have compared directly the ability of native and recombinant cofilins from Dictyostelium to sever F-actin. Our results demonstrate that native cofilin has a higher level of severing activity than recombinant cofilin. Significantly, the measurement of cofilin's severing activity by two independent methods, direct visualization with an improved light microscope assay and by scoring of the number of pointed ends by DNase I binding, clearly shows that both native and recombinant cofilins sever F-actin but to different extents. The severing activity in preparations of recombinant cofilin is variable depending on the method of preparation and, in some cases, is difficult to detect by microscopy assays. This latter point is particularly significant because it may lead to the conclusion that cofilin severs weakly or not at all depending on its method of isolation.
据报道，丝切蛋白通过切断肌动蛋白丝以增加解聚末端的数量，或者通过增加肌动蛋白单体从F-肌动蛋白上的解离速率而不增加丝末端的数量，来交替地使F-肌动蛋白解聚。我们直接比较了盘基网柄菌的天然丝切蛋白和重组丝切蛋白切断F-肌动蛋白的能力。我们的结果表明，天然丝切蛋白的切断活性水平高于重组丝切蛋白。值得注意的是，通过两种独立方法测量丝切蛋白的切断活性，即使用改进的光学显微镜检测法直接观察以及通过DNase I结合对尖末端数量进行计数，清楚地表明天然丝切蛋白和重组丝切蛋白都能切断F-肌动蛋白，但程度不同。重组丝切蛋白制剂中的切断活性因制备方法而异，在某些情况下，通过显微镜检测很难检测到。后一点尤为重要，因为这可能导致得出丝切蛋白根据其分离方法切断能力弱或根本不切断的结论。
