Lagrutta A A, Bond C T, Xia X M, Pessia M, Tucker S, Adelman J P
Vollum Institute for Advanced Biomedical Research, Oregon Health Sciences University, Portland 97201-3098, USA.
Jpn Heart J. 1996 Sep;37(5):651-60. doi: 10.1536/ihj.37.651.
A PCR-based cloning strategy was used to identify novel subunits of the two-transmembrane domain inward rectifier potassium channel family from rat brain, heart, and skeletal muscle. When expressed in Xenopus oocytes, two of these clones (Kir4.1 and Kir2.3) gave rise to inwardly rectifying potassium currents. Two-electrode voltage clamp commands to potentials negative to EK evoked inward potassium-selective currents which rapidly reached a peak amplitude and then relaxed to a steady-state level. Differences in the extent of current relaxation, the degree of rectification, and the voltage-dependent block by external cesium were detected. Two other members of this family (Kir5.1 and Kir3.4) did not produce macroscopic currents, when expressed by themselves, yet both subunits modified the currents when coexpressed with other specific members of the Kir family. Expression of chimeric subunits between Kir4.1 and either Kir5.1 or Kir3.4 suggested that the transmembrane domains determine the specificity of subunit heteropolymerization, while the C-terminal domains contribute to alterations in activation kinetics and rectification. Expression of covalently linked subunits demonstrated that the relative subunit positions, as well as stoichiometry, affect heteromeric channel activity.
采用基于聚合酶链反应（PCR）的克隆策略，从大鼠脑、心脏和骨骼肌中鉴定两跨膜结构域内向整流钾通道家族的新亚基。当在非洲爪蟾卵母细胞中表达时，其中两个克隆（Kir4.1和Kir2.3）产生内向整流钾电流。向负于EK的电位施加双电极电压钳指令，可诱发内向钾选择性电流，该电流迅速达到峰值幅度，然后松弛至稳态水平。检测到电流松弛程度、整流程度以及外部铯对电压依赖性阻滞方面的差异。该家族的另外两个成员（Kir5.1和Kir3.4）单独表达时不产生宏观电流，但与Kir家族的其他特定成员共表达时，两个亚基均能修饰电流。Kir4.1与Kir5.1或Kir3.4之间嵌合亚基的表达表明，跨膜结构域决定亚基异源聚合的特异性，而C末端结构域则影响激活动力学和整流的改变。共价连接亚基的表达表明，亚基的相对位置以及化学计量比会影响异源通道活性。
