Effect of phosphatidylserine on unitary conductance and Ba2+ block of the BK Ca2+-activated K+ channel: re-examination of the surface charge hypothesis.
Effect of phosphatidylserine on unitary conductance and Ba2+ block of the BK Ca2+-activated K+ channel: re-examination of the surface charge hypothesis.
复制标题
磷脂酰丝氨酸对BK Ca2+活化的K+通道的单位电导和BA2+块的影响：表面电荷假说的重新检查。
DOI：
10.1085/jgp.200208746
复制
发表时间：
2003-05
影响因子：
3.8
通讯作者：
Moczydlowski, Edward
中科院分区：
文献类型：
--
作者：
Park, Jin Bong;Kim, Hee Jeong;Ryu, Pan Dong;Moczydlowski, Edward
BK钙激活的K+通道纳入平面双层组成的带负电荷的磷脂，如磷脂酰丝氨酸（PS）或磷脂酰肌醇（PI）的结果在一个大的增强单位电导（gch）相比，BK通道形成的中性两性离子脂质，磷脂酰乙醇胺（PE）的双层。PS或PI对gch的增强作用与KCl浓度呈负相关，从10 mM KCl时的70%降至1，000 mM KCl时的8%。该效应先前通过表面电荷假设来解释（Moczydlowski，E.，O.阿尔瓦雷斯角，澳-地Vergara和R.拉托雷。1985. J. 83：273-282），其将电导增强归因于通道入口附近局部K+浓度的增加。为了验证这一假设，我们测量了外部和内部的Ba 2+，二价阳离子，预计强烈响应于表面静电的变化块的动力学。我们观察到很少或没有影响PS上的离散阻断动力学外部和内部的Ba 2+在100 mM KCl和只有一个小的增强离散和快速块外部Ba 2+在PS-含膜在20 mM KCl。模型计算的有效表面电位感测的K+传导和Ba 2 +-阻断反应使用的Gouy-Chapman-Stern理论的脂质表面电荷不借给支持一个简单的静电机制，预测当地阳离子浓度的价依赖性增加。结果表明，BK通道的传导孔与脂质表面静电绝缘，可能与脂质头部基团的横向分离距离（>20 μ m）。PS对Ba 2+的表观缔合和解离速率的影响的缺乏表明，K+电导的脂质调制优先通过选择性过滤器区域的构象变化来耦合，该区域确定该通道相对于其他阳离子的高K+通量速率。我们讨论了可能的机制，阴离子脂质的影响，在特定的分子相互作用的磷脂记录的KcsA细菌钾通道和一般膜的物理性质，提出通过能量学的双层应力调节膜蛋白构象的背景下。
Incorporation of BK Ca2+–activated K+ channels into planar bilayers composed of negatively charged phospholipids such as phosphatidylserine (PS) or phosphatidylinositol (PI) results in a large enhancement of unitary conductance (gch) in comparison to BK channels in bilayers formed from the neutral zwitterionic lipid, phospatidylethanolamine (PE). Enhancement of gch by PS or PI is inversely dependent on KCl concentration, decreasing from 70% at 10 mM KCl to 8% at 1,000 mM KCl. This effect was explained previously by a surface charge hypothesis (Moczydlowski, E., O. Alvarez, C. Vergara, and R. Latorre. 1985. J. Membr. Biol. 83:273–282), which attributed the conductance enhancement to an increase in local K+ concentration near the entryways of the channel. To test this hypothesis, we measured the kinetics of block by external and internal Ba2+, a divalent cation that is expected to respond strongly to changes in surface electrostatics. We observed little or no effect of PS on discrete blocking kinetics by external and internal Ba2+ at 100 mM KCl and only a small enhancement of discrete and fast block by external Ba2+ in PS-containing membranes at 20 mM KCl. Model calculations of effective surface potential sensed by the K+ conduction and Ba2+-blocking reactions using the Gouy-Chapman-Stern theory of lipid surface charge do not lend support to a simple electrostatic mechanism that predicts valence-dependent increase of local cation concentration. The results imply that the conduction pore of the BK channel is electrostatically insulated from the lipid surface, presumably by a lateral distance of separation (>20 Å) from the lipid head groups. The lack of effect of PS on apparent association and dissociation rates of Ba2+ suggest that lipid modulation of K+ conductance is preferentially coupled through conformational changes of the selectivity filter region that determine the high K+ flux rate of this channel relative to other cations. We discuss possible mechanisms for the effect of anionic lipids in the context of specific molecular interactions of phospholipids documented for the KcsA bacterial potassium channel and general membrane physical properties proposed to regulate membrane protein conformation via energetics of bilayer stress.