Jason L. Choy Laboratory of Single Molecule Biophysics, University of California, Berkeley, CA 94720.
Howard Hughes Medical Institute, University of California, Berkeley, CA 94720.
Proc Natl Acad Sci U S A. 2018 Jul 31;115(31):7961-7966. doi: 10.1073/pnas.1802736115. Epub 2018 Jul 16.
Subunits in multimeric ring-shaped motors must coordinate their activities to ensure correct and efficient performance of their mechanical tasks. Here, we study WT and arginine finger mutants of the pentameric bacteriophage φ29 DNA packaging motor. Our results reveal the molecular interactions necessary for the coordination of ADP-ATP exchange and ATP hydrolysis of the motor's biphasic mechanochemical cycle. We show that two distinct regulatory mechanisms determine this coordination. In the first mechanism, the DNA up-regulates a single subunit's catalytic activity, transforming it into a global regulator that initiates the nucleotide exchange phase and the hydrolysis phase. In the second, an arginine finger in each subunit promotes ADP-ATP exchange and ATP hydrolysis of its neighbor. Accordingly, we suggest that the subunits perform the roles described for GDP exchange factors and GTPase-activating proteins observed in small GTPases. We propose that these mechanisms are fundamental to intersubunit coordination and are likely present in other ring ATPases.
多聚体环状马达的亚基必须协调它们的活动，以确保其机械任务的正确和高效执行。在这里，我们研究了五聚体噬菌体 φ29 DNA 包装马达的 WT 和精氨酸指突变体。我们的结果揭示了协调马达双相机械化学循环中 ADP-ATP 交换和 ATP 水解所需的分子相互作用。我们表明，两种不同的调节机制决定了这种协调。在第一种机制中，DNA 上调单个亚基的催化活性，将其转化为全局调节剂，启动核苷酸交换相和水解相。在第二种机制中，每个亚基的精氨酸指促进其相邻亚基的 ADP-ATP 交换和 ATP 水解。因此，我们认为这些亚基执行了在小分子 GTP 酶中观察到的 GDP 交换因子和 GTPase 激活蛋白的作用。我们提出这些机制是亚基间协调的基础，并且可能存在于其他环 ATP 酶中。
