Iizuka Ryo, Yoshida Takao, Shomura Yasuhito, Miki Kunio, Maruyama Tadashi, Odaka Masafumi, Yohda Masafumi
Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei, Tokyo 184-8588, Japan.
J Biol Chem. 2003 Nov 7;278(45):44959-65. doi: 10.1074/jbc.M305484200. Epub 2003 Aug 14.
Group II chaperonins, found in archaea and in eukaryotic cytosol, do not have a co-chaperonin corresponding to GroES. Instead, it is suggested that the helical protrusion extending from the apical domain acts as a built-in lid for the central cavity and that the opening and closing of the lid is regulated by ATP binding and hydrolysis. However, details of this conformational change remain unclear. To investigate the conformational change associated with the ATP-driven cycle, we conducted protease sensitivity analyses and tryptophan fluorescence spectroscopy of alpha-chaperonin from a hyperthermophilic archaeum, Thermococcus strain KS-1. In the nucleotide-free or ADP-bound state, the chaperonin, especially in the helical protrusion region, was highly sensitive to proteases. Addition of ATP and ammonium sulfate induced the transition to the relatively protease-resistant form. The fluorescence intensity of the tryptophan residue introduced at the tip of the helical protrusion was enhanced by the presence of ATP or ammonium sulfate. We conclude that ATP binding induces the conformational change from the lid-open to lid-closed form in archaeal group II chaperonin.
第二类伴侣蛋白存在于古细菌和真核细胞质中，没有与GroES相对应的共伴侣蛋白。相反，有人提出从顶端结构域延伸出的螺旋突出物充当中央腔的内置盖子，并且盖子的打开和关闭由ATP结合和水解调节。然而，这种构象变化的细节仍不清楚。为了研究与ATP驱动循环相关的构象变化，我们对嗜热古细菌嗜热栖热菌KS-1菌株的α-伴侣蛋白进行了蛋白酶敏感性分析和色氨酸荧光光谱分析。在无核苷酸或ADP结合状态下，伴侣蛋白，尤其是在螺旋突出区域，对蛋白酶高度敏感。添加ATP和硫酸铵会诱导转变为相对抗蛋白酶的形式。在螺旋突出物顶端引入的色氨酸残基的荧光强度因ATP或硫酸铵的存在而增强。我们得出结论，ATP结合会诱导古细菌第二类伴侣蛋白从盖子打开形式转变为盖子关闭形式。
