Department of Biological Sciences and Bioengineering, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
Sci Rep. 2018 Aug 13;8(1):12055. doi: 10.1038/s41598-018-30257-4.
Plant aquaporins (AQPs) play vital roles in several physiological processes. Plasma membrane intrinsic proteins (PIPs) belong to the subfamily of plant AQPs. They are further subdivided into two closely related subgroups PIP1s and PIP2s. While PIP2 members are efficient water channels, PIP1s from some plant species have been shown to be functionally inactive. Aquaporins form tetramers under physiological conditions. PIP2s can enhance the water transport of PIP1s when they form hetero-tetramers. However, the role of monomer-monomer interface and the significance of specific residues in enhancing the water permeation of PIP1s have not been investigated at atomic level. We have performed all-atom molecular dynamics (MD) simulations of homo-tetramers and four different hetero-tetramers containing ZmPIP1;2 and ZmPIP2;5 from Zea mays. ZmPIP1;2 in a tetramer assembly will have two interfaces, one formed by transmembrane segments TM4 and TM5 and the other formed by TM1 and TM2. We have analyzed channel radius profiles, water transport and potential of mean force profiles of ZmPIP1;2 monomers. Results of MD simulations clearly revealed the influence of TM4-TM5 interface in modulating the water transport of ZmPIP1;2. MD simulations indicate the importance of I93 residue from the TM2 segment of ZmPIP2;5 for the increased water transport in ZmPIP1;2.
植物水通道蛋白（AQPs）在许多生理过程中发挥着重要作用。质膜内在蛋白（PIPs）属于植物 AQPs 的亚家族。它们进一步细分为两个密切相关的亚组 PIP1 和 PIP2。虽然 PIP2 成员是有效的水通道，但一些植物物种的 PIP1 已被证明在功能上是无活性的。在生理条件下，水通道蛋白形成四聚体。当形成异四聚体时，PIP2 可以增强 PIP1 的水运输。然而，单体-单体界面的作用以及特定残基在增强 PIP1 水渗透性方面的意义尚未在原子水平上进行研究。我们对来自玉米的ZmPIP1;2 和 ZmPIP2;5 的同源四聚体和四种不同的异四聚体进行了全原子分子动力学（MD）模拟。ZmPIP1;2 在四聚体组装中会有两个界面，一个由跨膜片段 TM4 和 TM5 形成，另一个由 TM1 和 TM2 形成。我们分析了 ZmPIP1;2 单体的通道半径分布、水传输和平均力势分布。MD 模拟结果清楚地揭示了 TM4-TM5 界面在调节 ZmPIP1;2 水传输中的影响。MD 模拟表明，ZmPIP2;5 的 TM2 片段中的 I93 残基对于增加 ZmPIP1;2 的水传输非常重要。
