Calcium regulatory proteins in plants; an NMR approach

钙离子作为第二信使在所有真核细胞中起着重要的作用。胞质Ca 2+水平的增加可以通过与调节性钙结合蛋白（如钙调蛋白（CaM））结合而起到触发装置的作用。集体的钙传感器蛋白可以重新定向细胞的生理状态。在植物中，胞质Ca 2+水平响应于各种非生物和生物胁迫（如寒冷、干旱、盐、创伤或植物病原体的存在）而增加。我们最近报道了各种植物钙调素和钙调素样蛋白结构域在其载脂蛋白和Ca ~（2+）饱和状态下的溶液结构。此外，我们还确定了三个高分辨率结构的复合物的钙调素异构体与三种植物蛋白，直接参与介导的应激反应：谷氨酸脱羧酶，MAPK-磷酸酶和液泡钙-ATP酶。在所有三种情况下，获得了新的复杂结构，这是以前没有见过的任何哺乳动物钙调素复合物，突出了意想不到的结构多样性的植物钙传感器蛋白家族。最近的基因组测序工作已经揭示，所有植物都具有大量种类的CaM、CaM样蛋白和CaM样蛋白结构域。例如，植物（和原生动物）含有一类独特的蛋白激酶（通常称为CDPK和CCaMK），这些蛋白激酶在其他生物体中没有发现。这些植物特异性酶含有它们自己的整合的CaM样结构域，其调节它们的活性。我们计划解决一些最独特的调控结构域的三维结构，以找出它们与钙、其蛋白质靶点或其他钙传感器蛋白相互作用的方式如何不同。此外，我们将完成我们的研究高度分歧钙调素样蛋白，在植物的盐胁迫反应中发挥作用。最后，我们将研究一个不寻常的膜锚定版本的钙调素，已被发现在各种植物。对于这项研究计划，我们将继续使用核磁共振（NMR）光谱作为我们的主要-但不是唯一的-实验工具，以获得有关这些蛋白质及其复合物在溶液状态下的详细结构和动力学信息。

Calcium plays an important role as a secondary messenger in all eukaryotic cells. An increase in the cytosolic Ca2+ level can act like a trigger device by binding to regulatory calcium-binding proteins, such as calmodulin (CaM). Collectively the calcium-sensor proteins can redirect the physiological status of a cell. In plants the cytosolic Ca2+ level increases in response to various abiotic and biotic stresses such as cold, drought, salt, wounding or the presence of plant pathogens. We have recently reported the solution structures of various plant CaM's and CaM-like protein domains in their apo and Ca2+-saturated states. Moreover we have also determined three high-resolution structures of complexes of a CaM isoform with three plant proteins that are directly involved in mediating the stress response: glutamate decarboxylase, MAPK-phosphatase and a vacuolar calcium-ATPase. In all three cases novel complex structures were obtained, which had not been seen before for any mammalian CaM complexes, highlighting unexpected structural diversity of the plant calcium-sensor protein family. Recent genome sequencing efforts have revealed that all plants possess a large variety of CaM's, CaM-like proteins and CaM-like protein domains. For example, plants (and protozoa) contain a unique class of protein kinases (commonly known as the CDPK's and the CCaMK's) that are not found in other organisms. These plant-specific enzymes contain their own integrated CaM-like domains, which modulate their activity. We plan to solve the three-dimensional structures of some of the most distinct regulatory domains to find out how they differ in the way they interact with calcium, their protein targets, or other calcium-sensor proteins. Moreover we will complete our studies of a highly divergent CaM-like protein that plays a role in the salt stress response in plants. Finally we will study an unusual membrane anchored version of CaM that has been detected in various plants. For this research program we will continue to use Nuclear Magnetic Resonance (NMR) spectroscopy as our main -but not exclusive- experimental tool, to obtain detailed structural and dynamic information about these proteins and their complexes in the solution state.