C-TYPE INACTIVATION OF A VOLTAGE-GATED K+ CHANNEL OCCURS BY A COOPERATIVE MECHANISM
C-TYPE INACTIVATION OF A VOLTAGE-GATED K+ CHANNEL OCCURS BY A COOPERATIVE MECHANISM
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DOI：
10.1016/s0006-3495(95)79963-5
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发表时间：
1995-09-01
影响因子：
3.4
通讯作者：
DEUTSCH, C
中科院分区：
文献类型：
--
作者：
PANYI, G;SHENG, ZF;DEUTSCH, C
淋巴细胞电压门控K+通道Kv1.3通过C型过程失活。我们已经阐明了这个过程中使用的野生型和突变体（A413 V）Kv1.3同源和异源多聚体电流在哺乳动物淋巴表达系统的动力学分析的分子基础。野生型和A413 V同源四聚体电流测得的失活时间常数的中位数分别为204和4 ms。这些亚基的共表达产生异源多聚体通道，其表现出介于野生型和A413 V同源多聚体之间的失活动力学。我们已经考虑了几种模型，其中每个亚基独立或合作产生所观察到的失活动力学。合作模型提供了很好的适合任何异源多聚体组成的亚基的数据，清楚地区分它从独立的模型。在合作模型中，通道的开放和失活状态之间的自由能的差异是不变的亚基组成，等于类似于1.5千卡/摩尔。每个亚基对开放和失活状态之间转变的活化自由能的贡献相等，A413 V亚基使失活（和从失活恢复）的自由能势垒降低约0.6 kcal/mol。我们的结果与一个物理模型一致，在该模型中，通道的外口在C型失活期间收缩（G。Yellen，D. Sodickson，T. Chen和M. E. Jurman，1994，Biophys. J. 66：1068-1075）。
The lymphocyte voltage-gated K+ channel, Kv1.3, inactivates by a C-type process. We have elucidated the molecular basis for this process using a kinetic analysis of wild-type and mutant (A413V) Kv1.3 homo- and heteromultimeric currents in a mammalian lymphoid expression system. The medians of the measured inactivation time constants for wild-type and A413V homotetrameric currents are 204 and 4 ms, respectively. Co-expression of these subunits produces heteromultimeric channels manifesting inactivation kinetics intermediate between those of wild-type and A413V homomultimers. We have considered several models in which each subunit acts either independently or cooperatively to produce the observed inactivation kinetics. The cooperative model gives excellent fits to the data for any heteromultimeric composition of subunits, clearly distinguishing it from the independent models. In the cooperative model, the difference in free energy between the open and inactivated states of the channel is invariant with subunit composition and equals similar to 1.5 kcal/mol. Each subunit contributes equally to the activation free energy for transitions between open and inactivated states, with an A413V subunit decreasing the free energy barrier for inactivation (and for recovery from inactivation) by similar to 0.6 kcal/mol. Our results are consistent with a physical model in which the outer mouth of the channel constricts during C-type inactivation (G. Yellen, D. Sodickson, T. Chen, and M. E. Jurman, 1994, Biophys. J. 66:1068-1075).