Meera P, Wallner M, Jiang Z, Toro L
Dept of Anesthesiology, University of California, Los Angeles 90095-1778, USA.
FEBS Lett. 1996 Mar 11;382(1-2):84-8. doi: 10.1016/0014-5793(96)00151-2.
KV,Ca beta subunit dramatically increases the apparent calcium sensitivity of the alpha subunit of MaxiK channels when probed in the micromolar [Ca2+]i range. Analysis in a wide range of [Ca2+]i revealed that this functional coupling is exquisitely modulated by [Ca2+]i. Ca2+ ions switch MaxiK alpha+beta complex into a functionally coupled state at concentrations beyond resting [Ca2+]i. At [Ca2+] < or = 100 nM, MaxiK activity becomes independent of Ca2+, is purely voltage-activated, and its functional coupling with its beta subunit is released. The functional switch develops at [Ca2+]i that occur during cellular excitation, providing the molecular basis of how MaxiK channels regulate smooth muscle excitability and neurotransmitter release.
当在微摩尔浓度的细胞内钙离子浓度范围内进行检测时，钾钙通道β亚基会显著提高大电导钙激活钾通道（MaxiK通道）α亚基的表观钙敏感性。在广泛的细胞内钙离子浓度范围内进行分析发现，这种功能偶联受到细胞内钙离子浓度的精确调控。钙离子在浓度超过静息细胞内钙离子浓度时，会将MaxiKα+β复合物转变为功能偶联状态。当细胞内钙离子浓度≤100 nM时，MaxiK活性变得与钙离子无关，完全由电压激活，并且其与β亚基的功能偶联被解除。这种功能转换发生在细胞兴奋期间出现的细胞内钙离子浓度水平上，为MaxiK通道如何调节平滑肌兴奋性和神经递质释放提供了分子基础。
