Department of Pharmacology, Northwestern University, Feinberg School of Medicine, Chicago, United States.
Molecular Medicine, Hospital for Sick Children, Toronto, Canada.
Elife. 2020 Oct 30;9:e60751. doi: 10.7554/eLife.60751.
Sulfur-aromatic interactions occur in the majority of protein structures, yet little is known about their functional roles in ion channels. Here, we describe a novel molecular motif, the M101 gate latch, which is essential for gating of human Orai1 channels via its sulfur-aromatic interactions with the F99 hydrophobic gate. Molecular dynamics simulations of different Orai variants reveal that the gate latch is mostly engaged in open but not closed channels. In experimental studies, we use metal-ion bridges to show that promoting an M101-F99 bond directly activates Orai1, whereas disrupting this interaction triggers channel closure. Mutational analysis demonstrates that the methionine residue at this position has a unique combination of length, flexibility, and chemistry to act as an effective latch for the phenylalanine gate. Because sulfur-aromatic interactions provide additional stabilization compared to purely hydrophobic interactions, we infer that the six M101-F99 pairs in the hexameric channel provide a substantial energetic contribution to Orai1 activation.
硫芳相互作用存在于大多数蛋白质结构中，但人们对其在离子通道中的功能作用知之甚少。在这里，我们描述了一个新的分子模体，即 M101 门闩，它通过与 F99 疏水门的硫芳相互作用对于人类 Orai1 通道的门控是必不可少的。不同 Orai 变体的分子动力学模拟表明，门闩主要与开放但非关闭的通道结合。在实验研究中，我们使用金属离子桥证明促进 M101-F99 键直接激活 Orai1，而破坏这种相互作用会触发通道关闭。突变分析表明，该位置的蛋氨酸残基具有独特的长度、灵活性和化学性质组合，可以作为苯丙氨酸门的有效闩。因为硫芳相互作用比纯疏水相互作用提供了额外的稳定性，我们推断六聚体通道中的六个 M101-F99 对为 Orai1 的激活提供了大量的能量贡献。
