Harrington M A, Gunderson K L, Kopito R R
Department of Biological Sciences, Stanford University, Stanford, California 94305-5020, USA.
J Biol Chem. 1999 Sep 24;274(39):27536-44. doi: 10.1074/jbc.274.39.27536.
Gating of the cystic fibrosis Cl(-) channel requires hydrolysis of ATP by its nucleotide binding folds, but how this process controls the kinetics of channel gating is poorly understood. In the present work we show that the kinetics of channel gating and presumably the rate of ATP hydrolysis depends on the species of divalent cation present and the oxidation state of the protein. With Ca(2+) as the dominant divalent cation instead of Mg(2+), the open burst duration of the channel is increased approximately 20-fold, and this change is reversible upon washout of Ca(2+). In contrast, "soft" divalent cations such as Cd(2+) interact covalently with cystic fibrosis transmembrane conductance regulator (CFTR). These metals decrease both opening and closing rates of the channel, and the effects are not reversed by washout. Oxidation of CFTR channels with a variety of oxidants resulted in a similar slowing of channel gating. In contrast, reducing agents had the opposite effect, increasing both opening and closing rates of the channel. In cell-attached patches, CFTR channels exhibit both oxidized and reduced types of gating, raising the possibility that regulation of the redox state of the channel may be a physiological mode of control of CFTR channel activity.
囊性纤维化氯离子通道的门控需要其核苷酸结合结构域水解ATP，但该过程如何控制通道门控的动力学却知之甚少。在本研究中，我们发现通道门控的动力学以及推测的ATP水解速率取决于存在的二价阳离子种类和蛋白质的氧化状态。以Ca(2+)作为主要二价阳离子而非Mg(2+)时，通道的开放爆发持续时间增加约20倍，且在洗去Ca(2+)后这种变化是可逆的。相反，“软”二价阳离子如Cd(2+)与囊性纤维化跨膜电导调节因子（CFTR）发生共价相互作用。这些金属降低了通道的开放和关闭速率，且冲洗后这些效应不会逆转。用多种氧化剂氧化CFTR通道会导致通道门控类似地减慢。相反，还原剂则有相反的作用，增加了通道的开放和关闭速率。在细胞贴附片膜中，CFTR通道表现出氧化型和还原型两种门控，这增加了通道氧化还原状态的调节可能是CFTR通道活性的一种生理控制模式的可能性。
