Renart María Lourdes, Giudici Ana Marcela, Coll-Díez Carlos, González-Ros José M, Poveda José A
IDiBE-Instituto de Investigación, Desarrollo e Innovación en Biotecnología Sanitaria de Elche, Universidad Miguel Hernández, 03202 Elche, Spain.
Biomedicines. 2023 May 5;11(5):1376. doi: 10.3390/biomedicines11051376.
Here, we report an allosteric effect of an anionic phospholipid on a model K channel, KcsA. The anionic lipid in mixed detergent-lipid micelles specifically induces a change in the conformational equilibrium of the channel selectivity filter (SF) only when the channel inner gate is in the open state. Such change consists of increasing the affinity of the channel for K, stabilizing a conductive-like form by maintaining a high ion occupancy in the SF. The process is highly specific in several aspects: First, lipid modifies the binding of K, but not that of Na, which remains unperturbed, ruling out a merely electrostatic phenomenon of cation attraction. Second, no lipid effects are observed when a zwitterionic lipid, instead of an anionic one, is present in the micelles. Lastly, the effects of the anionic lipid are only observed at pH 4.0, when the inner gate of KcsA is open. Moreover, the effect of the anionic lipid on K binding to the open channel closely emulates the K binding behaviour of the non-inactivating E71A and R64A mutant proteins. This suggests that the observed increase in K affinity caused by the bound anionic lipid should result in protecting the channel against inactivation.
在此，我们报道了一种阴离子磷脂对模型钾通道KcsA的变构效应。仅当通道内门处于开放状态时，混合去污剂 - 脂质胶束中的阴离子脂质才会特异性地诱导通道选择性过滤器（SF）的构象平衡发生变化。这种变化包括增加通道对钾的亲和力，通过在SF中保持高离子占有率来稳定类似传导的形式。该过程在几个方面具有高度特异性：首先，脂质改变钾的结合，但不改变钠的结合，钠的结合不受影响，排除了仅仅是阳离子吸引的静电现象。其次，当胶束中存在两性离子脂质而非阴离子脂质时，未观察到脂质效应。最后，仅在pH 4.0且KcsA内门开放时才观察到阴离子脂质的效应。此外，阴离子脂质对开放通道上钾结合的影响紧密模拟了非失活的E71A和R64A突变蛋白的钾结合行为。这表明，由结合的阴离子脂质引起的观察到的钾亲和力增加应导致保护通道免于失活。
