Wang Qin, Chen YaYu, Li ShengPing, Yang WenDi, Sun LiFang, Jang MeiQin, Wu XiuLing, Wang QianChao, Chen Lifei, Wu YunKun
State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, 155 Yangqiao West Road, Fuzhou 350002, China.
University of Chinese Academy of Sciences, Beijing 100049, China.
Comput Struct Biotechnol J. 2020 Mar 30;18:821-833. doi: 10.1016/j.csbj.2020.03.023. eCollection 2020.
RGLG1 is an E3 ubiquitin ligase in that participates in ABA signaling and regulates apical dominance. Here, we present crystal structures of RGLG1 VWA domain, revealing two novel calcium ions binding sites (NCBS1 and NCBS2). Furthermore, the structures with guided mutagenesis in NCBS1 prove that Ca ions play important roles in controlling conformational change of VWA, which is stabilized in open state with Ca bound and converted to closed state after Ca removal. This allosteric regulation mechanism is distinct from the ever reported one involving the C-terminal helix in integrin α and β I domains. The mutation of a key residue in NCBS2 do not abolish its Ca-binding potential, with no conformational change. MD simulations reveals that open state of RGLG1 VWA has higher ligand affinity than its closed state, consisting with integrin. Structural comparison of ion-free-MIDAS with Mg-MIDAS reveals that Mg binding to MIDAS does not induce conformational change. With acquisition of first structure of plant VWA domain in both open state and closed state, we carefully analyze the conformational change and propose a totally new paradigm for its transition of open-closed states, which will be of great value for guiding future researches on VWA proteins and their important biological significance.
RGLG1是一种E3泛素连接酶，参与脱落酸信号传导并调节顶端优势。在此，我们展示了RGLG1 VWA结构域的晶体结构，揭示了两个新的钙离子结合位点（NCBS1和NCBS2）。此外，在NCBS1中进行定点诱变的结构证明，钙离子在控制VWA的构象变化中起重要作用，钙离子结合时VWA稳定在开放状态，去除钙离子后转变为关闭状态。这种变构调节机制不同于以往报道的涉及整合素α和β I结构域中C末端螺旋的机制。NCBS2中一个关键残基的突变并不消除其钙离子结合潜力，且没有构象变化。分子动力学模拟表明，RGLG1 VWA的开放状态比其关闭状态具有更高的配体亲和力，这与整合素一致。无离子-MIDAS与镁-MIDAS的结构比较表明，镁与MIDAS结合不会诱导构象变化。随着首次获得植物VWA结构域在开放状态和关闭状态下的结构，我们仔细分析了构象变化，并提出了一个全新的开放-关闭状态转变范式，这将对指导未来关于VWA蛋白及其重要生物学意义的研究具有重要价值。
