Hydrogen peroxide (H2O2) transport by aquaporins (AQP) is a critical feature for cellular redox signaling. However, the H2O2 permeation mechanism through these channels remains poorly understood. Through functional assays, two Plasma membrane Intrinsic Protein (PIP) AQP from Medicago truncatula, MtPIP2;2 and MtPIP2;3 have been identified as pH-gated channels capable of facilitating the permeation of both water (H2O) and H2O2. Employing a combination of unbiased and enhanced sampling molecular dynamics simulations, we investigated the key barriers and translocation mechanisms governing H2O2 permeation through these AQP in both open and closed conformational states. Our findings reveal that both H2O and H2O2 encounter their primary permeation barrier within the selectivity filter (SF) region of MtPIP2;3. In addition to the SF barrier, a second energetic barrier at the NPA (asparagine-proline-alanine) region that is more restrictive for the passage of H2O2 than for H2O, was found. This behavior can be attributed to a dissimilar geometric arrangement and hydrogen bonding profile between both molecules in this area. Collectively, these findings suggest mechanistic heterogeneity in H2O and H2O2 permeation through PIPs.

中文翻译：

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过氧化氢和水通过质膜内在蛋白水通道蛋白的渗透机制。


水通道蛋白 (AQP) 传输的过氧化氢 (H2O2) 是细胞氧化还原信号传导的关键特征。然而，H2O2 通过这些通道的渗透机制仍然知之甚少。通过功能测定，来自蒺藜苜蓿的两个质膜内在蛋白 (PIP) AQP MtPIP2;2 和 MtPIP2;3 已被鉴定为 pH 门控通道，能够促进水 (H2O) 和 H2O2 的渗透。通过结合无偏和增强采样分子动力学模拟，我们研究了控制 H2O2 在开放和闭合构象状态下通过这些 AQP 渗透的关键障碍和易位机制。我们的研究结果表明，H2O 和 H2O2 都会在 MtPIP2 的选择性过滤器 (SF) 区域内遇到其主要渗透屏障；3。除了 SF 屏障之外，还发现了 NPA（天冬酰胺-脯氨酸-丙氨酸）区域的第二个能量屏障，它对 H2O2 的通过比对 H2O 的限制更严格。这种行为可归因于该区域中两个分子之间不同的几何排列和氢键分布。总的来说，这些发现表明 H2O 和 H2O2 通过 PIP 的渗透存在机械异质性。