Structural Studies of the Potassium Channel KCa3.1

项目摘要 KCa3.1，也称为SK 4或IK 1，是小至中电导钾家族的成员， 人体内的钾离子通道（KCa2.1-2.3，KCa3.1）。KCa3.1在T细胞激活中起着至关重要的作用， 钾维持负的膜电位，允许额外的钙流入。KCa3.1是一种 炎症性肠病如克罗恩病和溃疡性结肠炎的潜在治疗靶点， 器官移植排斥反应KCa3.1（和KCa2.1-2.3）是同源四聚体，通过钙激活 与钙调蛋白（CaM）结合，钙调蛋白与通道（CaM）的胞质区域组成性相关 结合结构域，CaMBD）。KCa3.1激活的一个新特征是磷酸化的额外要求 在CaMBD下游的特定组氨酸残基（His 358），通过NDPK-B（核苷二磷酸） 激酶-B）。虽然组氨酸磷酸化在双组分信号系统中得到了很好的表征， 在原核生物中，真核生物中组氨酸磷酸化的功能后果才刚刚开始被研究。 明白最近，我们发现KCa3.1的组氨酸磷酸化对于释放铜是必要的， 通道的抑制。在该应用中，提出冷冻-EM研究来阐明分子生物学。 KCa3.1受钙和组氨酸磷酸化调节的机制。

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.