Urbanik E, Ware B R
Department of Chemistry, Syracuse University, New York 13244.
Arch Biochem Biophys. 1989 Feb 15;269(1):181-7. doi: 10.1016/0003-9861(89)90098-2.
The concentration dependences of the activities of cytochalasin B, D, E, and H in capping and cleaving actin filaments have been assayed using fluorescence photobleaching recovery. Filament capping was detected by the increase in mobile G-actin. Cytochalasin D (CD) showed the strongest filament capping activity, with an apparent dissociation constant from filament ends of 50 nM. The order of capping activity was CD greater than CH greater than CE much greater than CB. Filament cleavage was detected by the increase in the diffusion coefficients of actin filaments. By this criterion the order of filament cleavage activity was CD, CE greater than CH much greater than CB. Cytochalasin B shows some activity in cleavage of filaments over a concentration range (0-100 microM) at which it shows no appreciable capping activity. This activity, together with results from other groups, is interpreted to mean that CB binds to protomers within the filament, but not to the barbed end. The reversal of activities for CH and CE, combined with the activity profile of CB, constitute the strongest evidence to date that there is more than one cytochalasin binding site on the actin molecule.
利用荧光光漂白恢复技术测定了细胞松弛素B、D、E和H在封端和切割肌动蛋白丝过程中活性的浓度依赖性。通过可移动的G-肌动蛋白的增加来检测丝封端。细胞松弛素D（CD）表现出最强的丝封端活性，其从丝末端的表观解离常数为50 nM。封端活性顺序为CD＞CH＞CE＞＞CB。通过肌动蛋白丝扩散系数的增加来检测丝切割。据此，丝切割活性顺序为CD、CE＞CH＞＞CB。细胞松弛素B在一定浓度范围（0 - 100 microM）内对丝切割表现出一些活性，在此浓度范围内它没有明显的封端活性。这种活性，连同其他研究小组的结果，被解释为意味着CB与丝内的原聚体结合，但不与带刺末端结合。CH和CE活性的反转，以及CB的活性图谱，构成了迄今为止关于肌动蛋白分子上存在多个细胞松弛素结合位点的最有力证据。
