Structural Studies of the Potassium Channel KCa3.1

项目总结 KCa3.1，也被称为SK4或IK1，是中小电导钾家族的成员 人类的通道(KCa2.1-2.3，KCa3.1)。KCa3.1在T细胞外流激活中的重要作用 钾以维持负膜电位，从而允许额外的钙内流。KCa3.1是一种 治疗炎症性肠病的潜在靶点，如克罗恩病和溃疡性结肠炎 器官移植排斥反应。KCa3.1(和KCa2.1-2.3)是同分异构体，通过钙激活 与钙调素(CaM)的结合，它与通道的细胞质区域(CaM)构成相关 结合结构域，CaMBD)。KCa3.1激活的一个新特征是需要额外的磷酸化 通过NDPK-B(二磷酸核苷)在CaMBD下游的特定组氨酸残基(His358)的作用 KK-B)。尽管组氨酸磷酸化在双组分信号系统中得到了很好的表征 原核生物，真核生物中组氨酸磷酸化的功能后果才刚刚开始 明白了。最近，我们发现KCa3.1的组氨酸磷酸化对于铜的释放是必要的 对通道的抑制。在这一应用中，冷冻-EM研究被用来阐明分子 KCa3.1受钙和组氨酸磷酸化调控的机制。

PROJECT SUMMARY KCa3.1, also known as SK4 or IK1, is a member of a family of small- to intermediate-conductance potassium channels in humans (KCa2.1–2.3, KCa3.1). KCa3.1 plays a crucial role in T-cell activation by effluxing potassium to maintain a negative membrane potential that allows for additional calcium influx. KCa3.1 is a potential therapeutic target for inflammatory bowel diseases such as Crohn's disease and ulcerative colitis and for organ transplant rejection. KCa3.1 (and KCa2.1–2.3) is homotetrameric and activated through calcium binding to calmodulin (CaM), which is constitutively associated with a cytoplasmic region of the channels (CaM binding domain, CaMBD). A novel feature of KCa3.1 activation is the additional requirement of phosphorylation of a specific histidine residue (His358), just downstream of the CaMBD, by NDPK-B (nucleoside diphosphate kinase-B). Although histidine phosphorylation is well characterized in two-component signaling systems in prokaryotes, the functional consequences of histidine phosphorylation in eukaryotes are just beginning to be understood. Recently, we showed that histidine phosphorylation of KCa3.1 is necessary to relieve copper inhibition of the channel. In this application, cryo-EM studies are proposed to elucidate the molecular mechanisms by which KCa3.1 is regulated by calcium and histidine phosphorylation.