Facultad de Farmacia y Bioquímica, Departamento de Fisicomatemática, Universidad de Buenos Aires, Argentina.
Instituto de Química y Fisicoquímica Biológica (IQUIFIB), Facultad de Farmacia y Bioquímica, CONICET, Universidad de Buenos Aires, Argentina.
FEBS J. 2022 Jan;289(1):246-261. doi: 10.1111/febs.16134. Epub 2021 Aug 3.
Plant PIP aquaporins play a central role in controlling plant water status. The current structural model for PIP pH-gating states that the main pH sensor is located in loopD and that all the mobile cytosolic elements participate in a complex interaction network that ensures the closed structure. However, the precise participation of the last part of the C-terminal domain (CT) in PIP pH gating remains unknown. This last part has not been resolved in PIP crystal structures and is a key difference between PIP1 and PIP2 paralogues. Here, by a combined experimental and computational approach, we provide data about the role of CT in pH gating of Beta vulgaris PIP. We demonstrate that the length of CT and the positive charge located among its last residues modulate the pH at which the open/closed transition occurs. We also postulate a molecular-based mechanism for the differential pH sensing in PIP homo- or heterotetramers by performing atomistic molecular dynamics simulations (MDS) on complete models of PIP tetramers. Our findings show that the last part of CT can affect the environment of loopD pH sensors in the closed state. Results presented herein contribute to the understanding of how the characteristics of CT in PIP channels play a crucial role in determining the pH at which water transport through these channels is blocked, highlighting the relevance of the differentially conserved very last residues in PIP1 and PIP2 paralogues.
植物质膜内在蛋白水通道在控制植物水分状态方面发挥着核心作用。目前的 PIP pH 门控结构模型表明，主要的 pH 传感器位于环 D，所有可移动的细胞质元件都参与一个复杂的相互作用网络，以确保其封闭结构。然而，C 端结构域（CT）的最后一部分在 PIP pH 门控中的精确参与仍然未知。在 PIP 晶体结构中，最后一部分尚未解决，这是 PIP1 和 PIP2 同源物之间的关键区别。在这里，我们通过结合实验和计算方法，提供了关于 CT 在 Beta vulgaris PIP pH 门控中的作用的数据。我们证明了 CT 的长度和位于其最后残基之间的正电荷调节了开放/关闭转变发生的 pH 值。我们还通过对 PIP 同源或异四聚体的完整模型进行原子分子动力学模拟（MDS），提出了一种用于 PIP 同或异四聚体中 pH 差异感应的分子基础机制。我们的研究结果表明，CT 的最后一部分可以影响环 D pH 传感器在封闭状态下的环境。本文的研究结果有助于理解 PIP 通道中 CT 的特性如何在决定这些通道中水运输被阻断的 pH 值方面发挥关键作用，突出了 PIP1 和 PIP2 同源物中差异保守的最后残基的相关性。
