O'Donoghue S I, Miki M, dos Remedios C G
Department of Anatomy, University of Sydney, NSW, Australia.
Arch Biochem Biophys. 1992 Feb 14;293(1):110-6. doi: 10.1016/0003-9861(92)90372-4.
We define conditions under which the two C-terminal residues of actin, Cys-374 and Phe-375, can be selectively removed by proteolysis with trypsin. This modification had little effect on the secondary structure of actin detected by Fourier-transform infrared spectroscopy. However, removing these residues caused small but significant decreases in the critical concentration of actin, in its ability to activate myosin ATPase, and in its interaction with tropomyosin and troponin. Removing residues 374-375 caused dramatic changes in the actin filament as seen by electron microscopy. The filaments had a much greater and more irregular curvature and were intertwined into disordered multifilament bundles. Removing 374-375 also significantly lowered the flow viscosity of filamentous-actin solutions. These data suggest an increase in the flexibility and fragility of the filament, supporting the idea that the C-terminus forms one of the major intermonomer contacts in the filament.
我们定义了肌动蛋白C端的两个残基，即半胱氨酸-374和苯丙氨酸-375，可被胰蛋白酶进行蛋白水解选择性去除的条件。这种修饰对傅里叶变换红外光谱检测到的肌动蛋白二级结构影响很小。然而，去除这些残基会导致肌动蛋白的临界浓度、激活肌球蛋白ATP酶的能力以及与原肌球蛋白和肌钙蛋白的相互作用出现虽小但显著的降低。如电子显微镜所见，去除残基374 - 375会使肌动蛋白丝发生显著变化。这些丝具有更大且更不规则的曲率，并相互缠绕形成无序的多丝束。去除374 - 375也显著降低了丝状肌动蛋白溶液的流动粘度。这些数据表明丝的柔韧性和脆性增加，支持了C端形成丝中主要单体间接触之一的观点。
