牛嗜铬粒细胞膜中钾离子通道的证据：单通道特性及可能的生物能量学意义。

Evidence for a K+ channel in bovine chromaffin granule membranes: single-channel properties and possible bioenergetic significance.

作者信息

Ashley R H, Brown D M, Apps D K, Phillips J H

机构信息

Department of Biochemistry, University of Edinburgh, UK.

出版信息

Eur Biophys J. 1994;23(4):263-75. doi: 10.1007/BF00213576.

DOI:10.1007/BF00213576

PMID:7528657

Abstract

A K+ channel was incorporated into voltage-clamped planar lipid bilayers from bovine chromaffin granules and resealed granule membranes ("ghosts"). It was not incorporated from plasma membrane-rich fractions from the adrenal medulla. The channel had a conductance of approximately 400 pS in symmetric 450 mM KCl, with the permeability sequence K+ > Rb+ > Cs+ > Na+ > Li+, and was insensitive to both Ca2+ and charybdotoxin. It exhibited complex gating kinetics, consistent with the presence of multiple open and closed states, and its gating was voltage-dependent. The channels appeared to incorporate into bilayers with the same orientation, and were blocked from one side (the side of vesicle addition) by 0.2-1 mM TEA+. The block was slightly voltage-dependent. Acidification of resealed granule membranes in response to external ATP (which activated the vacuolar-type ATPase) was significantly reduced in the presence of 1 mM intralumenal TEACl (with 9 mM KCl), and parallel measurements with the potential-sensitive dye Oxonol V showed that such vesicles tended to develop higher internal-positive membrane potentials than control vesicles containing only 10 mM KCl. 1 mM TEA+ had no effect on proton-pumping activity when applied externally, and did not directly affect either the proton-pumping or ATP hydrolytic activity of the partially-purified ATPase. These results suggest that chromaffin granule membranes contain a TEA(+)-sensitive K+ channel which may have a role in regulating the vesicle membrane potential.

摘要

一种钾离子通道被整合到来自牛嗜铬颗粒和重新封闭的颗粒膜（“鬼膜”）的电压钳制平面脂质双分子层中。它未从肾上腺髓质富含质膜的组分中整合进去。该通道在对称的450 mM KCl中电导约为400 pS，通透顺序为K⁺＞Rb⁺＞Cs⁺＞Na⁺＞Li⁺，并且对Ca²⁺和蝎毒素均不敏感。它表现出复杂的门控动力学，与存在多个开放和关闭状态一致，并且其门控是电压依赖性的。这些通道似乎以相同的方向整合到双分子层中，并且从一侧（添加囊泡的一侧）被0.2 - 1 mM四乙铵离子（TEA⁺）阻断。这种阻断略微依赖电压。在存在1 mM腔内TEACl（含9 mM KCl）的情况下，响应外部ATP（激活液泡型ATP酶）重新封闭的颗粒膜的酸化显著降低，并且用电压敏感染料氧化苯乙烯基花青V进行的平行测量表明，与仅含有10 mM KCl的对照囊泡相比，此类囊泡倾向于产生更高的内部正膜电位。当外部施加1 mM TEA⁺时，对质子泵活性没有影响，并且不直接影响部分纯化的ATP酶的质子泵或ATP水解活性。这些结果表明嗜铬颗粒膜含有一种对TEA⁺敏感的钾离子通道，其可能在调节囊泡膜电位中起作用。