Coexpression of α and β subunits of the rod cyclic GMP-gated channel restores native sensitivity to cyclic AMP:: Role of D604/N1201
Coexpression of α and β subunits of the rod cyclic GMP-gated channel restores native sensitivity to cyclic AMP:: Role of D604/N1201
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DOI：
10.1016/s0006-3495(00)76680-x
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发表时间：
2000-03-01
影响因子：
3.4
通讯作者：
Bennett, N
中科院分区：
文献类型：
--
作者：
Pagès, F;IIdefonse, M;Bennett, N
牛视杆细胞通道的β wt和α wt亚基的共表达恢复了天然通道的两个特征：对cAMP的更高敏感性和通过低cAMP浓度增强cGMP诱导的电流。为了测试对cAMP的敏感性增加是否是由于天冬酰胺残基（N1201）的不带电荷性质，如先前所建议的那样，天冬酰胺残基（N1201）位于β亚基中天冬氨酸D 604的位置（Varnum等人，1995年，神经元。15：619-625），我们比较了来自突变通道（α D 604 N、α D 604 N/β wt和α wt/β N1201 D）的野生型（α wt和α wt/β wt）酸的电流。结果表明，对cAMP的敏感性和cAMP增强作用部分但不完全由β亚基中残基1201的电荷决定。α亚基中的D 604 N突变以及在较小程度上β wt亚基与α wt亚基的共表达与α wt通道相比降低了cGMP的开放概率。用MWC变构模型（Monod，Wyman，Changeux的模型; Monod等人，1965，J. Mel. 12：88-118）表明α亚基中的D 604 N突变以及α和β亚基的共组装改变cAMP门控的自由能多于cAMP结合的自由能。
Coexpression of the beta wt and alpha wt subunits of the bovine rod channel restores two characteristics of the native channels: higher sensitivity to cAMP and potentiation of cGMP-induced currents by low cAMP concentrations. To test whether the increased sensitivity to cAMP is due to the uncharged nature of the asparagine residue (N1201) situated in place of aspartate D604 in the beta subunit as previously suggested (Varnum et al., 1995, Neuron. 15:619-625), we compared currents from wild-type (alpha wt and alpha wt/beta wt) acid from mutated channels (alpha D604N, alpha D604N/beta wt, and alpha wt/beta N1201D). The results show that the sensitivity to cAMP and cAMP potentiation is partly but-not entirely determined by the charge of residue 1201 in the beta subunit. The D604N mutation in the alpha subunit and, to a lesser extent, coexpression of the beta wt subunit with the alpha wt subunit reduce the open probability for cGMP compared to that of the alpha wt channel. Interpretation of the data with the MWC allosteric model (model of Monod, Wyman, Changeux; Monod et al,, 1965, J. Mel. Biol. 12:88-118) suggests that the D604N mutation in the alpha subunits and coassembly of alpha and beta subunits alter the free energy of gating by cAMP more than that of cAMP binding.