Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
Cell. 2018 Jan 25;172(3):605-617.e11. doi: 10.1016/j.cell.2017.12.010. Epub 2018 Jan 11.
The bacterial chaperonin GroEL and its cofactor, GroES, form a nano-cage for a single molecule of substrate protein (SP) to fold in isolation. GroEL and GroES undergo an ATP-regulated interaction cycle to close and open the folding cage. GroEL consists of two heptameric rings stacked back to back. Here, we show that GroEL undergoes transient ring separation, resulting in ring exchange between complexes. Ring separation occurs upon ATP-binding to the trans ring of the asymmetric GroEL:7ADP:GroES complex in the presence or absence of SP and is a consequence of inter-ring negative allostery. We find that a GroEL mutant unable to perform ring separation is folding active but populates symmetric GroEL:GroES complexes, where both GroEL rings function simultaneously rather than sequentially. As a consequence, SP binding and release from the folding chamber is inefficient, and E. coli growth is impaired. We suggest that transient ring separation is an integral part of the chaperonin mechanism.
细菌伴侣蛋白 GroEL 及其辅助因子 GroES 形成纳米笼，可使单个底物蛋白 (SP) 分子在隔离状态下折叠。GroEL 和 GroES 经历一个 ATP 调节的相互作用循环来关闭和打开折叠笼。GroEL 由两个背对背堆叠的七聚体环组成。在这里，我们表明 GroEL 经历瞬时环分离，导致复合物之间的环交换。在存在或不存在 SP 的情况下，ATP 结合到不对称 GroEL：7ADP：GroES 复合物的跨环上会引发环分离，这是环间负变构的结果。我们发现，无法进行环分离的 GroEL 突变体具有折叠活性，但会聚集对称的 GroEL：GroES 复合物，其中两个 GroEL 环同时而不是顺序地发挥作用。结果，SP 结合和从折叠腔释放效率低下，并且大肠杆菌的生长受到损害。我们认为，瞬时环分离是伴侣蛋白机制的一个组成部分。
