PDF(Pubmed)
Abstract：
Transmembrane signaling by plant receptor kinases (RKs) has long been thought to involve reciprocal trans-phosphorylation of their intracellular kinase domains. The fact that many of these are pseudokinase domains, however, suggests that additional mechanisms must govern RK signaling activation. Non-catalytic signaling mechanisms of protein kinase domains have been described in metazoans, but information is scarce for plants. Recently, a non-catalytic function was reported for the leucine-rich repeat (LRR)-RK subfamily XIIa member EFR (elongation factor Tu receptor) and phosphorylation-dependent conformational changes were proposed to regulate signaling of RKs with non-RD kinase domains. Here, using EFR as a model, we describe a non-catalytic activation mechanism for LRR-RKs with non-RD kinase domains. EFR is an active kinase, but a kinase-dead variant retains the ability to enhance catalytic activity of its co-receptor kinase BAK1/SERK3 (brassinosteroid insensitive 1-associated kinase 1/somatic embryogenesis receptor kinase 3). Applying hydrogen-deuterium exchange mass spectrometry (HDX-MS) analysis and designing homology-based intragenic suppressor mutations, we provide evidence that the EFR kinase domain must adopt its active conformation in order to activate BAK1 allosterically, likely by supporting αC-helix positioning in BAK1. Our results suggest a conformational toggle model for signaling, in which BAK1 first phosphorylates EFR in the activation loop to stabilize its active conformation, allowing EFR in turn to allosterically activate BAK1.
摘要：
长期以来，人们一直认为植物受体激酶（RKs）的跨膜信号传导涉及其细胞内激酶结构域的相互反式磷酸化。事实上，其中许多是假激酶结构域，然而,表明其他机制必须控制RK信号激活。蛋白激酶结构域的非催化信号机制已经在后生动物中被描述，但是植物的信息很少。最近,据报道,富亮氨酸重复序列(LRR)-RK亚家族XIIa成员EFR(延伸因子Tu受体)具有非催化功能,并提出磷酸化依赖性构象变化来调节具有非RD激酶结构域的RK信号传导.这里,使用EFR作为模型，我们描述了具有非RD激酶结构域的LRR-RKs的非催化活化机制。EFR是一种活性激酶，但是激酶死亡的变体保留了增强其共受体激酶BAK1/SERK3（油菜素类固醇不敏感的1相关激酶1/体细胞胚胎发生受体激酶3）的催化活性的能力。应用氢-氘交换质谱（HDX-MS）分析并设计基于同源性的基因内抑制突变，我们提供的证据表明，EFR激酶结构域必须采用其活性构象才能变构激活BAK1，可能通过支持BAK1中的αC-螺旋定位。我们的结果表明信号传导的构象切换模型，其中BAK1首先磷酸化激活环中的EFR以稳定其活性构象，允许EFR反过来变构激活BAK1。
