Highsmith S
Biochemistry. 1978 Jan 10;17(1):22-6. doi: 10.1021/bi00594a004.
The association of fluorescently labeled heavy meromyosin (HMM) and F-actin was measured by time-resolved fluorescence depolarization. The effects of varying the protein concentrations, temperature, KCl concentration, and pH were determined. Measurements of HMM mobility supported a model of no interaction between the two heads in the absence of actin. Measurements of actin binding, when compared with results for myosin subfragment I, indicated that the two heads of HMM do not bind independently in the rigor complex. This could result from actin-transmitted negative cooperativity or from steric inhibition due to the structure of HMM. For HMM and actin in 0.15 7 kcl at 25 degrees C: Ka = 3.9 X 10(7) M-1, deltaHco' = 36 +/- 2 J M-1, deltaSco' = 0.26 +/- 0.02 kJ M-1 K-1; the slope of ln Ka vs. [KCl]1/2 = -3.88 and the pH of maximum association was 6.9.
通过时间分辨荧光偏振测量荧光标记的重酶解肌球蛋白（HMM）与F-肌动蛋白的结合。测定了改变蛋白质浓度、温度、KCl浓度和pH的影响。对HMM迁移率的测量支持了在没有肌动蛋白的情况下两个头部之间不存在相互作用的模型。与肌球蛋白亚片段I的结果相比，肌动蛋白结合的测量表明，在强直复合物中HMM的两个头部不是独立结合的。这可能是由于肌动蛋白传递的负协同作用或由于HMM的结构导致的空间抑制。对于在25℃下0.15 7 kcl中的HMM和肌动蛋白：Ka = 3.9×10(7) M-1，deltaHco' = 36±2 J M-1，deltaSco' = 0.26±0.02 kJ M-1 K-1；ln Ka对[KCl]1/2的斜率 = -3.88，最大结合的pH为6.9。
