Casein kinase 1 (CK1) is an evolutionarily conserved protein kinase family among eukaryotes. Studies in non‐plants have shown CK1‐dependent divergent biological processes, but the collective knowledge regarding the biological roles of plant CK1 lags far behind other members of the Eukarya. One reason for this is that plants have many more genes encoding CK1 than do animals. To accelerate our understanding of the plant CK1 family, a strong CK1 inhibitor that efficiently inhibits multiple members of the CK1 protein family in vivo (i.e., in planta) is required. Here, we report a novel, specific, and effective CK1 inhibitor in Arabidopsis. Using circadian period‐lengthening activity as an estimation of the CK1 inhibitor effect in vivo, we performed a structure–activity relationship study of analogues of the CK1 inhibitor PHA767491 (1,5,6,7‐tetrahydro‐2‐(4‐pyridinyl)‐4H‐pyrrolo[3,2‐c]pyridin‐4‐one hydrochloride). A propargyl group at the pyrrole nitrogen atom (AMI‐212) or a bromine atom at the pyrrole C3 position (AMI‐23) had stronger CK1 inhibitory activity than PHA767491. A hybrid molecule of AMI‐212 and AMI‐23 (AMI‐331) was about 100‐fold more inhibitory than the parent molecule PHA767491. Affinity proteomics using an AMI‐331 probe showed that the targets of AMI‐331 inhibition are mostly CK1 kinases. As such, AMI‐331 is a potent and selective CK1 inhibitor that shows promise in the research of CK1 in plants.

中文翻译：

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拟南芥酪蛋白激酶 1 家族新型抑制剂的结构-功能研究。

酪蛋白激酶 1 (CK1) 是真核生物中进化保守的蛋白激酶家族。对非植物的研究表明，CK1 依赖性的不同生物过程，但有关植物 CK1 生物学作用的集体知识远远落后于真核生物的其他成员。原因之一是植物比动物拥有更多的编码 CK1 的基因。为了加速我们对植物CK1家族的了解，需要一种能够在体内（即植物体内）有效抑制CK1蛋白家族多个成员的强效CK1抑制剂。在此，我们报道了拟南芥中一种新型、特异且有效的 CK1 抑​​制剂。使用昼夜节律延长活性作为体内 CK1 抑​​制剂效应的估计，我们对 CK1 抑​​制剂 PHA767491（1,5,6,7-四氢-2-(4-吡啶基）类似物进行了结构-活性关系研究‐4H-吡咯并[3,2-c]吡啶-4-酮盐酸盐）。吡咯氮原子上的炔丙基（AMI-212）或吡咯C3位上的溴原子（AMI-23）比PHA767491具有更强的CK1抑制活性。AMI-212 和 AMI-23 的混合分子 (AMI-331) 的抑制作用比母体分子 PHA767491 高约 100 倍。使用 AMI-331 探针的亲和蛋白质组学表明 AMI-331 抑制的靶标主要是 CK1 激酶。因此，AMI-331 是一种有效的选择性 CK1 抑​​制剂，在植物 CK1 研究中显示出前景。