Chen Haijun, Kim Leo A, Rajan Sindhu, Xu Shuhua, Goldstein Steve A N
Department of Pediatrics, Boyer Center for Molecular Medicine, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA.
Neuron. 2003 Sep 25;40(1):15-23. doi: 10.1016/s0896-6273(03)00570-1.
I(Ks) voltage-gated K(+) channels contain four pore-forming KCNQ1 subunits and MinK accessory subunits in a number that has been controversial. Here, I(Ks) channels assembled naturally by monomer subunits are compared to those with linked subunits that force defined stoichiometries. Two strategies that exploit charybdotoxin (CTX)-sensitive subunit variants are applied. First, CTX on rate, off rate, and equilibrium affinity are found to be the same for channels of monomers and those with a fixed 2:4 MinK:KCNQ1 valence. Second, 3H-CTX and an antibody are used to directly quantify channels and MinK subunits, respectively, showing 1.97 +/- 0.07 MinK per I(Ks) channel. Additional MinK subunits do not enter channels of monomeric subunits or those with fixed 2:4 valence. We conclude that two MinK subunits are necessary, sufficient, and the norm in I(Ks) channels. This stoichiometry is expected for other K(+) channels that contain MinK or MinK-related peptides (MiRPs).
I(Ks)电压门控钾通道包含四个成孔的KCNQ1亚基和数量存在争议的MinK辅助亚基。在此，将由单体亚基自然组装的I(Ks)通道与具有强制确定化学计量比的连接亚基的通道进行比较。应用了两种利用对蝎毒素（CTX）敏感的亚基变体的策略。首先，发现单体通道和具有固定2:4 MinK:KCNQ1化合价的通道的CTX结合速率、解离速率和平衡亲和力相同。其次，分别使用3H-CTX和一种抗体直接定量通道和MinK亚基，结果显示每个I(Ks)通道有1.97±0.07个MinK亚基。额外的MinK亚基不会进入单体亚基通道或具有固定2:4化合价的通道。我们得出结论，两个MinK亚基是I(Ks)通道所必需的、足够的且是常态的。对于其他包含MinK或MinK相关肽（MiRPs）的钾通道，预计也有这种化学计量比。
