Kirsch G E, Drewe J A, De Biasi M, Hartmann H A, Brown A M
Department of Anesthesiology, Baylor College of Medicine, Houston, Texas 77030.
J Biol Chem. 1993 Jul 5;268(19):13799-804.
The aqueous pore (P-region) of homotetrameric voltage-gated K+ channels has been modeled as a radially symmetrical eight-stranded antiparallel beta-barrel to which each of the four subunits contributes equally. This model has hydrogen bonding between residues located on adjacent subunits and predicts that subunit interactions might have functional consequences. Previously we have used point mutations and an electrophysiological assay to detect functional interactions between a pair of residues at positions 369 and 374 in the P-region, but we could not distinguish between intra- and intersubunit interactions. In the present paper, we present evidence for interaction across subunit boundaries after co-injecting two cRNAs encoding subunits differing from each other at either position 369 or 374. Comparison of the phenotypes of homo- and heterotetrameric channels suggests that pore residues residing in adjacent subunits form a closely packed structure which determines both ion conductance and stability of the open state of the channel. Our results are consistent with a structure in which pore residues 369 and 374 are located in close proximity on adjacent antiparallel strands to allow both intra- and intersubunit interactions.
同四聚体电压门控钾离子通道的水相孔道（P 区）已被模拟为径向对称的八链反平行β桶结构，四个亚基对其贡献相同。该模型显示相邻亚基上的残基之间存在氢键，并预测亚基间相互作用可能具有功能影响。此前我们利用点突变和电生理检测方法，检测了 P 区 369 位和 374 位一对残基之间的功能相互作用，但无法区分亚基内和亚基间的相互作用。在本文中，我们展示了共注射编码在 369 位或 374 位存在差异的亚基的两种 cRNA 后，跨亚基边界相互作用的证据。对同四聚体和异四聚体通道表型的比较表明，相邻亚基中的孔道残基形成紧密堆积的结构，该结构决定了离子电导以及通道开放状态的稳定性。我们的结果与一种结构相符，即孔道残基 369 和 374 位于相邻反平行链上彼此靠近的位置，从而允许亚基内和亚基间的相互作用。
