Imbrici Paola, Grottesi Alessandro, D'Adamo Maria Cristina, Mannucci Roberta, Tucker Stephen J, Pessia Mauro
Section of Human Physiology, Department of Internal Medicine, University of Perugia School of Medicine, Perugia, Italy.
Channels (Austin). 2009 Jan-Feb;3(1):39-45. doi: 10.4161/chan.3.1.7548. Epub 2009 Jan 3.
Shaker-like (KV1.1) channels contain a highly conserved Pro-Val-Pro (PVP) motif at the base of S6 that produces a kink in the S6 helices and provides a flexible element thought to be essential for channel gating. The role of proline-induced kinks in transmembrane helices is well known, but the contribution of the small hydrophobic valine between these two prolines is not known, and interestingly, Shab-like (KV2.1) channels possess an isoleucine at this position (PIP). Here we show that the exact nature of this central hydrophobic residue within the PXP motif confers unique functional properties to KV1 channels, including changes in activation and deactivation kinetics, voltage-dependent properties and open probabilities, but single-channel conductance and cell expression levels are not affected. In support of these functional changes, molecular dynamic simulations demonstrate that valine and isoleucine contribute differently to S6 flexibility within this motif. These results therefore indicate that the nature of the central hydrophobic residue in the PXP motif is an important functional determinant of KV channel gating by contributing, at least in part, to the relative flexibility of this motif.
类Shaker（KV1.1）通道在S6的基部含有一个高度保守的脯氨酸-缬氨酸-脯氨酸（PVP）基序，该基序在S6螺旋中产生一个扭结，并提供一个被认为对通道门控至关重要的柔性元件。脯氨酸诱导的扭结在跨膜螺旋中的作用是众所周知的，但这两个脯氨酸之间的小疏水缬氨酸的作用尚不清楚，有趣的是，类Shab（KV2.1）通道在这个位置（PIP）有一个异亮氨酸。在这里，我们表明PXP基序内这个中心疏水残基的确切性质赋予了KV1通道独特的功能特性，包括激活和失活动力学、电压依赖性特性和开放概率的变化，但单通道电导和细胞表达水平不受影响。为支持这些功能变化，分子动力学模拟表明缬氨酸和异亮氨酸对该基序内S6的灵活性有不同贡献。因此，这些结果表明PXP基序中中心疏水残基的性质是KV通道门控的一个重要功能决定因素，至少部分是通过促成该基序的相对灵活性来实现的。
