van Huizen R, Czajkowsky D M, Shi D, Shao Z, Li M
Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
FEBS Lett. 1999 Aug 20;457(1):107-11. doi: 10.1016/s0014-5793(99)01021-2.
The Shaker type voltage-gated potassium (K+) channel consists of four pore-forming Kv alpha subunits. The channel expression and kinetic properties can be modulated by auxiliary hydrophilic Kv beta subunits via formation of heteromultimeric Kv alpha-Kv beta complexes. Because each (Kv alpha)4 could recruit more than one Kv beta subunit and different Kv beta subunits could potentially interact, the stoichiometry of alpha-beta and beta-beta complexes is therefore critical for understanding the functional regulation of Shaker type potassium channels. We expressed and purified Kv beta 2 subunit in Sf9 insect cells. The purified Kv beta 2, examined by atomic force and electron microscopy techniques, is found predominately as a square-shaped tetrameric complex with side dimensions of 100 x 100 A2 and height of 51 A. Thus, Kv beta 2 is capable of forming a tetramer in the absence of pore-forming alpha subunits. The center of the Kv beta 2 complex was observed to be the most heavily stained region, suggesting that this region could be part of an extended tubular structure connecting the inner mouth of the ion permeation pathway to the cytoplasmic environment.
摇椅型电压门控钾（K+）通道由四个形成孔道的Kvα亚基组成。通道的表达和动力学特性可通过辅助亲水性Kvβ亚基形成异源多聚体Kvα-Kvβ复合物来调节。由于每个（Kvα）4可招募一个以上的Kvβ亚基，且不同的Kvβ亚基可能相互作用，因此α-β和β-β复合物的化学计量对于理解摇椅型钾通道的功能调节至关重要。我们在Sf9昆虫细胞中表达并纯化了Kvβ2亚基。通过原子力显微镜和电子显微镜技术检测，纯化的Kvβ2主要呈现为方形四聚体复合物，边长为100×100 Å2，高度为51 Å。因此，Kvβ2在不存在形成孔道的α亚基的情况下能够形成四聚体。观察到Kvβ2复合物的中心是染色最深的区域，这表明该区域可能是连接离子渗透途径内口与细胞质环境的延伸管状结构的一部分。
