Temperature- dependent fold- switching mechanism of the circadian clock protein KaiB

• 成果类型: Article
• 署名作者: Zhang, Ning; Sood, Damini; Guo, Spencer C.; Chen, Nanhao; Antoszewski, Adam; Marianchuk, Tegan; Dey, Supratim; Xiao, Yunxian; Hong, Lu; Peng, Xiangda; Baxa, Michael; Partch, Carrie; Wang, Lee-Ping; Sosnick, Tobin R.; Dinner, Aaron R.; Liwang, Andy
• 署名单位: University of California System; University of California Merced; University of Chicago; University of Chicago; University of California System; University of California Davis; University of Chicago; University of Chicago; University of California System; University of California Santa Cruz; University of California System; University of California Merced; Chinese Academy of Sciences; Qingdao Institute of Bioenergy & Bioprocess Technology, CAS; Duke University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-11094
• DOI: 10.1073/pnas.2412327121
• 发表日期: 2024-12-17
• 关键词: cis-trans isomerization; accessible surface-areas; hammond behavior; atpase activity; l-proline; COMPENSATION; oscillator; domain; time; activation

摘要

The oscillator of the cyanobacterial circadian clock relies on the ability of the KaiB protein to switch reversibly between a stable ground- state fold (gsKaiB) and an unstable fold- switched fold (fsKaiB). Rare fold- switching events by KaiB provide a critical delay in the negative feedback loop of this posttranslational oscillator. In this study, we experimentally and computationally investigate the temperature dependence of fold switching and its mechanism. We demonstrate that the stability of gsKaiB increases with temperature compared to fsKaiB and that the Q10 value for the gsKaiB -> fsKaiB transition is nearly three times smaller than that for the reverse transition in a construct optimized for NMR studies. Simulations and native- state hydrogen- deuterium exchange NMR experiments suggest that fold switching can involve both partially and completely unfolded intermediates. The simulations predict that the transition state for fold switching coincides with isomerization of conserved prolines in the most rapidly exchanging region, and we confirm experimentally that proline isomerization is a rate- limiting step for fold switching. We explore the implications of our results for temperature compensation, a hallmark of circadian clocks, through a kinetic model.