Pressure effects on the cyanobacterial circadian clock

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K06530
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 43020:Structural biochemistry-related
• Research Institution: Ritsumeikan University
• Principal Investigator: Kitahara Ryo 立命館大学, 薬学部, 教授 (70512284)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 概日時計 / シアノバクテリア / 高圧 / ATPase

Outline of Final Research Achievements

Despite broad-scale adaptations of organisms across domains (from bacteria to animals) to various environmental conditions such as temperature, pressure, pH, and salt concentrations, the circadian clock is a shared characteristic as a fundamental timing device. However, the detailed molecular mechanism of each autonomously operating circadian clock remains unclear. The circadian clock of cyanobacteria is controlled by three proteins, KaiA, KaiB, KaiC, and ATP. While the circadian rhythm is inherently robust to temperature change, we found that KaiC phosphorylation cycles were accelerated from 22 h at 1 bar to 14 h at 200 bar and to 11 h at 400 bar, decreasing circadian-period length. This reduction resulted from pressure-induced enhancement of KaiC ATPase activity and allosteric effects. This relashionship was also investigated in the KaiC mutants, R393C and F470Y.

Free Research Field

構造生物学

Academic Significance and Societal Importance of the Research Achievements

ヒトを含めた地球上の生物は地球の自転に同調した生物リズムを有する。本研究では、最も構造生物学的研究が進んでいるシアノバクテリアの概日時計をモデルとして、その圧力効果を調べた。概日時計は３つのタンパク質KaiA, KaiB, KaiCとATPからなり、KaiCのリン酸化脱リン酸化のサイクルが約24時間の周期を示す。加圧により周期長が短縮すること、短縮はKaiCの有するATP加水分解活性(ATPase活性）の上昇と相関があることを見出した。活性化体積が負であること、つまり反応の遷移状態で体積が収縮することを示す。深海（高圧）など極限環境での生命現象の理解やその環境適応についての知見となる。