Hong Haiyan, Guo Zilong, Sun Hao, Yu Ping, Su Huanhuan, Ma Xuening, Chen Hu
Research Institute for Biomimetics and Soft Matter, Fujian Provincial Key Lab for Soft Functional Materials Research, Department of Physics, Xiamen University, Xiamen, 361005, China.
Center of Biomedical Physics, Wenzhou Institute, University of Chinese Academy of Sciences, Wenzhou, 325000, China.
Commun Chem. 2021 Nov 9;4(1):156. doi: 10.1038/s42004-021-00592-1.
Cold shock protein (Csp) is a typical two-state folding model protein which has been widely studied by biochemistry and single molecule techniques. Recently two-state property of Csp was confirmed by atomic force microscopy (AFM) through direct pulling measurement, while several long-lifetime intermediate states were found by force-clamp AFM. We systematically studied force-dependent folding and unfolding dynamics of Csp using magnetic tweezers with intrinsic constant force capability. Here we report that Csp mostly folds and unfolds with a single step over force range from 5 pN to 50 pN, and the unfolding rates show different force sensitivities at forces below and above ~8 pN, which determines a free energy landscape with two barriers and a transient intermediate state between them along one transition pathway. Our results provide a new insight on protein folding mechanism of two-state proteins.
冷休克蛋白（Csp）是一种典型的两态折叠模型蛋白，已被生物化学和单分子技术广泛研究。最近，通过直接拉伸测量，原子力显微镜（AFM）证实了Csp的两态特性，而力钳AFM则发现了几个长寿命中间态。我们使用具有固有恒力能力的磁镊系统地研究了Csp的力依赖性折叠和去折叠动力学。在此我们报告，在5 pN至50 pN的力范围内，Csp大多以单步进行折叠和去折叠，并且在低于和高于约8 pN的力下，去折叠速率显示出不同的力敏感性，这决定了一个具有两个势垒以及沿一条转变途径介于它们之间的一个瞬态中间态的自由能景观。我们的结果为两态蛋白的蛋白质折叠机制提供了新的见解。
