Rectifying electrical synapses (RESs) exist across animal species, but their rectification mechanism is largely unknown. We investigated why RESs between AVA premotor interneurons and A-type cholinergic motoneurons (A-MNs) in Caenorhabditis elegans escape circuit conduct junctional currents (I_j) only in the antidromic direction. These RESs consist of UNC-7 innexin in AVA and UNC-9 innexin in A-MNs. UNC-7 has multiple isoforms differing in the length and sequence of the amino terminus. In a heterologous expression system, only one UNC-7 isoform, UNC-7b, can form heterotypic gap junctions (GJs) with UNC-9 that strongly favor I_j in the UNC-9 to UNC-7 direction. Knockout of unc-7b alone almost eliminated the I_j, whereas AVA-specific expression of UNC-7b substantially rescued the coupling defect of unc-7 mutant. Neutralizing charged residues in UNC-7b amino terminus abolished the rectification property of UNC-7b/UNC-9 GJs. Our results suggest that the rectification property results from electrostatic interactions between charged residues in UNC-7b amino terminus.

整流电突触（RES）存在于各种动物物种中，但其整流机制很大程度上未知。我们研究了为什么秀丽隐杆线虫逃逸回路中 AVA 前运动中间神经元和 A 型胆碱能运动神经元 (A-MN) 之间的 RES仅在逆向方向传导连接电流 ( I _{j )。}这些RES由AVA中的UNC-7内联蛋白和A-MN中的UNC-9内联蛋白组成。UNC-7 具有多种异构体，其氨基末端的长度和序列不同。在异源表达系统中，只有一种 UNC-7 同种型 UNC-7b 可以与 UNC-9 形成异型间隙连接 (GJ)，在 UNC-9 到 UNC-7 方向上强烈支持 I j _。单独敲除unc-7b几乎消除了I _{j ，而UNC-7b的AVA特异性表达基本上挽救了}unc-7突变体的偶联缺陷。中和 UNC-7b 氨基末端的带电残基消除了 UNC-7b/UNC-9 GJ 的整流特性。我们的结果表明，整流特性是由 UNC-7b 氨基末端带电残基之间的静电相互作用引起的。