Chaperonins are biomolecular complexes that assist protein folding. Thermophilic Factor 55 (TF55) is a group II chaperonin found in the archaeal genus Sulfolobus that has α, β and γ subunits. Using cryo-electron microscopy, we have determined the structure of the β-only complex of S. solfataricus TF55 complexes to 3.6-4.2 Å resolution and a filamentous form to 5.2 Å resolution. The structures of the TF55β complexes formed in the presence of ADP or ATP highlighted an open state in which nucleotide exchange can occur before progressing in the refolding cycle. The structure of the filamentous state indicates how helical protrusions facilitate end-on-end interactions.

中文翻译：

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开放状态和丝状状态的Sulfolobus solfataricusTF55β伴侣蛋白的结构分析

伴侣蛋白是有助于蛋白质折叠的生物分子复合物。嗜热因子55（TF55）是古菌类Sulfolobus中发现的具有α，β和γ亚基的II类伴侣蛋白。使用冷冻电子显微镜，我们确定了S. solfataricus TF55复合物的仅β复合物的结构，分辨率为3.6-4.2Å，丝状形式的分子结构为5.2Å。在ADP或ATP存在下形成的TF55β复合物的结构突出显示了一种开放状态，在这种状态下核苷酸交换可以发生在重折叠周期之前。丝状状态的结构表明螺旋状突起如何促进端对端相互作用。