Pallotta B S
J Gen Physiol. 1985 Nov;86(5):601-11. doi: 10.1085/jgp.86.5.601.
Calcium-activated potassium channels from cultured rat skeletal muscle were treated with the protein-modifying reagent N-bromoacetamide (NBA) (0.3-1 mM) and studied in excised patches using patch-clamp techniques. After NBA treatment, channels opened only occasionally, and, in contrast to untreated channels, the open probability was no longer sensitive to intracellular surface calcium ions (1 nM to 100 microM). Channel activity did, however, exhibit a voltage dependence similar in direction and magnitude to that shown before NBA treatment (increasing e-fold with 19 mV depolarization). Distributions of open channel lifetimes revealed that NBA treatment virtually abolished openings of long duration, which suggests that this class of openings requires calcium sensitivity. These effects were not reversed by subsequent washing. Quantitatively similar open probability, voltage dependence, and open-interval distributions were observed in untreated channels in calcium-free medium. These results suggest that NBA removed a calcium-dependent component of channel opening, and that normal channels are able to open in the absence of significant intracellular calcium concentrations.
用蛋白质修饰试剂N-溴乙酰胺（NBA）（0.3 - 1 mM）处理培养的大鼠骨骼肌钙激活钾通道，并使用膜片钳技术在切除的膜片中进行研究。经NBA处理后，通道仅偶尔开放，与未处理的通道相比，开放概率不再对细胞内表面钙离子（1 nM至100 μM）敏感。然而，通道活性确实表现出与NBA处理前相似的电压依赖性，其方向和幅度相同（去极化19 mV时增加e倍）。开放通道寿命的分布表明，NBA处理实际上消除了长时间的开放，这表明这类开放需要钙敏感性。这些效应不会因随后的冲洗而逆转。在无钙培养基中未处理的通道中观察到了定量相似的开放概率、电压依赖性和开放间隔分布。这些结果表明，NBA去除了通道开放的钙依赖性成分，并且正常通道能够在没有显著细胞内钙浓度的情况下开放。
