Tobacman L S, Korn E D
J Biol Chem. 1982 Apr 25;257(8):4166-70.
Profilin inhibits the rate of nucleation of actin polymerization and the rate of filament elongation and also reduces the concentration of F-actin at steady state. Addition of profilin to solutions of F-actin causes depolymerization. The same steady state concentrations of polymerized and nonpolymerized actin are reached whether profilin is added before initiation of polymerization or after polymerization is complete. The KD for formation of the 1:1 complex between Acanthamoeba profilin and Acanthamoeba actin is in the range of 4 to 11 microM; the KD for the reaction between Acanthamoeba profilin and rabbit skeletal muscle actin is about 60 to 80 microM, irrespective of the concentrations of KCl or MgCl2. The critical concentration of actin for polymerization and the KD for the actin-profilin interaction are independent of each other; therefore, a change in the critical concentration of actin alters the amount of actin bound to profilin at steady state. As a consequence, the presence of profilin greatly amplifies the effects of small changes in the actin critical concentration on the concentration of F-actin. Profilin also inhibits the ATPase activity of monomeric actin, the profilin-actin complex being entirely inactive.
肌动蛋白结合蛋白抑制肌动蛋白聚合的成核速率和丝状体伸长速率，并且在稳态时还降低F-肌动蛋白的浓度。向F-肌动蛋白溶液中添加肌动蛋白结合蛋白会导致解聚。无论在聚合开始前还是聚合完成后添加肌动蛋白结合蛋白，都会达到相同的聚合态和非聚合态肌动蛋白的稳态浓度。棘阿米巴肌动蛋白结合蛋白与棘阿米巴肌动蛋白形成1:1复合物的解离常数（KD）在4至11微摩尔范围内；棘阿米巴肌动蛋白结合蛋白与兔骨骼肌肌动蛋白之间反应的KD约为60至80微摩尔，与氯化钾或氯化镁的浓度无关。肌动蛋白聚合的临界浓度与肌动蛋白-肌动蛋白结合蛋白相互作用的KD彼此独立；因此，肌动蛋白临界浓度的变化会改变稳态时与肌动蛋白结合蛋白结合的肌动蛋白量。结果，肌动蛋白结合蛋白的存在极大地放大了肌动蛋白临界浓度的微小变化对F-肌动蛋白浓度的影响。肌动蛋白结合蛋白还抑制单体肌动蛋白的ATP酶活性，肌动蛋白结合蛋白-肌动蛋白复合物完全无活性。
