Multimeric nature of voltage-gated proton channels
Multimeric nature of voltage-gated proton channels
复制标题
DOI：
10.1073/pnas.0801553105
复制
发表时间：
2008-07-01
影响因子：
11.1
通讯作者：
Larsson, H. Peter
中科院分区：
文献类型：
--
作者：
Koch, Hans P.;Kurokawa, Tatsuki;Larsson, H. Peter
电压门控钾通道由四个亚基组成，每个亚基都有一个孔结构域和一个电压传感结构域（VSD）。四个孔域聚集在一起形成一个中央孔，四个单独的 VSD 控制孔的门。最近，发现了一系列电压门控质子通道，例如 H-v 或仅电压传感器蛋白 (VSOP)，其包含单个 VSD 但没有孔结构域。假设 VSOP 通道是单体的，并且包含一个既充当 VSD 又充当孔域的 VSD。然而，目前尚不清楚仅包含 VSD 而不含孔结构域的蛋白质如何传导离子。使用荧光测量和免疫沉淀技术，我们在此表明 VSOP 通道表示为多聚体通道。此外，对具有共价连接亚基的构建体进行的 FRET 实验表明 VSOP 通道是二聚体。 VSOP 细胞质区域的截短减少了二聚化，表明二聚化主要是由细胞质蛋白质-蛋白质相互作用引起的。然而，这些 N 末端和 C 末端缺失的通道显示出较大的质子电流。因此，我们得出结论，尽管 VSOP 通道主要以二聚体形式在细胞膜中表达，但单个 VSOP 亚基可以独立地作为质子通道发挥作用。
Voltage-gated potassium channels are comprised of four subunits, and each subunit has a pore domain and a voltage-sensing domain (VSD). The four pore domains assemble to form one single central pore, and the four individual VSDs control the gate of the pore. Recently, a family of voltage-gated proton channels, such as H-v or voltage sensor only protein (VSOP), was discovered that contain a single VSD but no pore domain. it has been assumed that VSOP channels are monomeric and contain a single VSD that functions as both the VSD and the pore domain. It remains unclear, however, how a protein that contains only a VSD and no pore domain can conduct ions. Using fluorescence measurements and immunoprecipitation techniques, we show here that VSOP channels are expressed as multimeric channels. Further, FRET experiments on constructs with covalently linked subunits show that VSOP channels are dimers. Truncation of the cytoplasmic regions of VSOP reduced the dimerization, suggesting that the dimerization is caused mainly by cytoplasmic protein-protein interactions. However, these N terminus- and C terminus-deleted channels displayed large proton currents. Therefore, we conclude that even though VSOP channels are expressed mainly as dimers in the cell membrane, single VSOP subunits could function independently as proton channels.