A single amino acid in gamma-aminobutyric acid rho 1 receptors affects competitive and noncompetitive components of picrotoxin inhibition.
A single amino acid in gamma-aminobutyric acid rho 1 receptors affects competitive and noncompetitive components of picrotoxin inhibition.
复制标题
γ-氨基丁酸 rho 1 受体中的单个氨基酸影响印防己毒素抑制的竞争性和非竞争性成分。
DOI：
10.1073/pnas.92.25.11751
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发表时间：
1995
影响因子：
11.1
通讯作者：
Cutting,GR
中科院分区：
文献类型：
--
作者：
Wang,TL;Hackam,AS;Guggino,WB;Cutting,GR
已在视网膜中鉴定出一类荷包牡丹碱不敏感的γ-氨基丁酸（GABA）受体，GABAC。几条证据表明GABAC受体部分或全部由GABA rho亚基形成。这些受体响应GABA产生Cl-电流，但在许多方面与GABAA受体不同。印防己毒素是公认的GABAA受体的非竞争性拮抗剂，它对鲈鱼和牛视网膜中的GABAC受体和非洲爪蟾卵母细胞中表达的GABA rho 1受体具有竞争性和非竞争性拮抗作用。本研究的目的是确定印防己毒素抑制GABA rho 1受体的两种成分的分子基础。通过使用结构域交换和诱变策略，在印防己毒素的敏感性之间的差异rho 1和rho 2受体被定位到一个单一的氨基酸在推定的第二跨膜结构域。用在高度印防己毒素敏感的甘氨酸α和GABAA亚基中的类似位置发现的残基取代该氨基酸，使rho 1突变体的敏感性增加10至500倍。重要的是，印防己毒素抑制rho 1突变体受体的竞争性成分几乎被消除。这些研究结果表明，在GABA rho 1受体的推定通道域的氨基酸影响印防己毒素的敏感性和介导的激动剂结合的变构机制。
A class of bicuculline-insensitive gamma-aminobutyric acid (GABA) receptors, GABAC, has been identified in retina. Several lines of evidence indicate that GABAC receptors are formed partially or wholly of GABA rho subunits. These receptors generate a Cl- current in response to GABA but differ from GABAA receptors in a number of ways. Picrotoxin, widely accepted as a noncompetitive antagonist of GABAA receptors, displays competitive and noncompetitive antagonism of GABAC receptors in perch and bovine retina and GABA rho 1 receptors expressed in Xenopus oocytes. The aim of this study was to identify the molecular basis of the two components of picrotoxin inhibition of GABA rho 1 receptors. By using a domain-swapping and mutagenesis strategy, a difference in picrotoxin sensitivity between rho 1 and rho 2 receptors was localized to a single amino acid in the putative second transmembrane domain. Substitution of this amino acid with residues found in the analogous position in highly picrotoxin-sensitive glycine alpha and GABAA subunits increased the sensitivity of rho 1 mutants 10- to 500-fold. Importantly, the competitive component of picrotoxin inhibition of the rho 1 mutant receptors was almost eliminated. These findings demonstrate that an amino acid in the putative channel domain of GABA rho 1 receptors influences picrotoxin sensitivity and mediates agonist binding by an allosteric mechanism.