Kasai M, Kawasaki T
Department of Biophysical Engineering, Faculty of Engineering Science, Osaka University.
J Biochem. 1993 Mar;113(3):327-33. doi: 10.1093/oxfordjournals.jbchem.a124047.
The effect of ryanodine on the permeation of glucose, choline, and Ca2+ through the Ca2+ channel in sarcoplasmic reticulum vesicles was studied by means of the light scattering and/or the tracer method. Ryanodine had the same effect on the permeabilities of choline and Ca2+; low concentrations of ryanodine (10 microM) locked the channel in the open state, and high concentrations (100 microM) opened the channel transiently, which closed finally. Glucose became permeable on the ryanodine treatment even in the absence of KCl, although it was not permeable before the treatment when the channel was open. Submolar concentrations of KCl enhanced the glucose and choline permeability of the ryanodine-treated channel as well as the untreated one. Activators such as ATP and caffeine did not enhance the permeability of the treated channel in the open locked state, but inhibitors such as Mg2+ and ruthenium red closed the channel, although much higher concentrations were required than for the untreated channel. The maximal rates of choline and glucose permeation of the ryanodine-treated channel were lower than those of the untreated one attained in the presence of ATP and/or caffeine. This result is consistent with the fact that the single channel conductance after the ryanodine treatment decreased to 40-50% of the maximal conductance of the untreated one. This result suggests that the conformation of the channel opened by ryanodine was different from that with ATP or caffeine.
采用光散射和/或示踪法研究了ryanodine对葡萄糖、胆碱和Ca2+通过肌浆网囊泡中Ca2+通道渗透的影响。Ryanodine对胆碱和Ca2+的通透性有相同的影响；低浓度的ryanodine（10 microM）使通道锁定在开放状态，高浓度（100 microM）使通道短暂开放，最终关闭。即使在没有KCl的情况下，ryanodine处理后葡萄糖也变得可渗透，尽管在处理前通道开放时它是不可渗透的。亚摩尔浓度的KCl增强了ryanodine处理的通道以及未处理通道的葡萄糖和胆碱通透性。ATP和咖啡因等激活剂不会增强处于开放锁定状态的处理通道的通透性，但Mg2+和钌红等抑制剂会使通道关闭，尽管所需浓度比未处理通道高得多。Ryanodine处理的通道的胆碱和葡萄糖最大渗透速率低于在ATP和/或咖啡因存在下未处理通道的最大渗透速率。这一结果与ryanodine处理后单通道电导降至未处理通道最大电导的40 - 50%这一事实一致。该结果表明，ryanodine打开的通道构象与ATP或咖啡因打开的通道构象不同。
