Lehrer S S, Betteridge D R, Graceffa P, Wong S, Seidel J C
Biochemistry. 1984 Apr 10;23(8):1591-5. doi: 10.1021/bi00303a001.
In contrast to previous conformational studies with rabbit skeletal and cardiac tropomyosins, (i) when the cysteine side chains of chicken gizzard tropomyosin were reacted with 5,5'-dithiobis(2-nitrobenzoate), an interchain disulfide cross-link was not produced, (ii) when they were labeled with pyrenylmaleimide , excimer fluorescence was not observed, and (iii) when they were labeled with didansylcystine , a long-lived fluorescence component did not appreciably contribute to the fluorescence decay over a large temperature range including the major unfolding transition. In addition, the temperature dependence of the ellipticity at 222 nm did not reveal a pretransition prior to the main helix unfolding transition. This indicates that gizzard tropomyosin does not exhibit a localized chain-open state in the region of its cysteine residues, analogous to that seen with cardiac and skeletal tropomyosins, nor in any other region of the molecule. As a consequence, these observations suggest that gizzard tropomyosin is more rigid than striated tropomyosin.
与之前对兔骨骼肌和心肌原肌球蛋白的构象研究不同，（i）当鸡砂囊原肌球蛋白的半胱氨酸侧链与5,5'-二硫代双（2-硝基苯甲酸）反应时，未产生链间二硫键交联；（ii）当用芘马来酰亚胺标记它们时，未观察到准分子荧光；（iii）当用双丹磺酰胱氨酸标记它们时，在包括主要解折叠转变的较大温度范围内，一个长寿命荧光成分对荧光衰减没有明显贡献。此外，222nm处椭圆率的温度依赖性在主要螺旋解折叠转变之前未显示出预转变。这表明砂囊原肌球蛋白在其半胱氨酸残基区域没有表现出类似于心肌和骨骼肌原肌球蛋白的局部链开放状态，在分子的任何其他区域也没有。因此，这些观察结果表明砂囊原肌球蛋白比横纹肌原肌球蛋白更刚性。
