摘要
Structural analysis of K+ channel pores suggests that the selectivity filter of the pore is an inherent sensor for extracellular K+ \((\mathrm{K}_{\mathrm{o}}^{{+}});\) channels seem to be inactivated at low \(\mathrm{K}_{\mathrm{o}}^{{+}}\) because of a destabilization of the conducting state and a collapse of the pore. In the present study, the effect of depleting \(\mathrm{K}_{\mathrm{o}}^{{+}}\) on the activity of a plant K+ channel, KAT1, from Arabidopsis thaliana was investigated. This channel is thought to be insensitive to \(\mathrm{K}_{\mathrm{o}}^{{+}}.\) The channel was therefore expressed in mammalian HEK293 cells and measured with patch clamp technology in the whole cell configuration. The effect of \(\mathrm{K}_{\mathrm{o}}^{{+}}\) depletion on channel activity was monitored from the tail currents before, during, and after washing \(\mathrm{K}_{\mathrm{o}}^{{+}}\) from the medium. The data show that a depletion of \(\mathrm{K}_{\mathrm{o}}^{{+}}\) results in a decrease in channel conductance, irrespective of whether K+ is simply removed or replaced by either Na+ or Li+. Quantitative analysis suggests that the channel has two binding sites for K+ with the dissociation constant in the order of 20 μM. This high sensitivity of the channel to \(\mathrm{K}_{\mathrm{o}}^{{+}}\) could serve as a safety mechanism, which inactivates the channel at low \(\mathrm{K}_{\mathrm{o}}^{{+}}\) and, in this way, prevents leakage of K+ from the cells via this type of channel.
摘要译文
K +孔道孔隙的结构分析表明孔隙的选择性过滤器是细胞外钾离子的固有传感器（{mathrm {K} _ {\\ mathrm { ø}} ^ {{+}}）;\\）通道看起来是在低的（\\ mathrm {K} _ {\\ mathrm {o}} ^ {{+}} \\）中失活的，因为导电状态的不稳定和孔隙的塌陷。在目前的研究中，消耗来自拟南芥的植物K + +通道KAT1的活性的影响是（来源：调查。这个通道被认为对\\（\\ mathrm {K} _ {\\ mathrm {o}} ^ {{+}}不敏感。\\）因此通道在哺乳动物HEK293细胞中表达，并且在全细胞构型中用膜片钳技术测量。从尾电流监测在通道活动之前，期间和之后的通道活动的消耗的效果，并从介质中清洗\\（\\ mathrm {K} _ {\\ mathrm {o}} ^ {{+}} \\）。数据显示，消耗的通道电导率降低，而不管K +是仅仅被去除还是被Na + +或Li + +取代。定量分析表明，通道具有两个K +的结合位点，其解离常数约为20μM。这个通道对信道的高度敏感性可以作为一个安全机制，使信道在低位（\\ mathrm {K} _ {\\ mathrm {o}} ^ {{+}} \\），这样，防止通过这种类型的通道从单元泄漏K +。
Brigitte Hertel ; Ferenc Horváth Search for other works by this author on: Oxford Academic; Barnabás Wodala Search for other works by this author on: Oxford Academic; Annette Hurst Search for other works by this author on: Oxford Academic; Anna Moroni Search for other works by this author on: Oxford Academic; Gerhard Thiel Search for other works by this author on: Oxford Academic. KAT1 inactivates at sub-millimolar concentrations of external potassium[J]. Journal of Experimental Botany, 2005,56(422): 3103–3110