The Calmodulin-related Calcium Sensor CML42 Plays a Role in Trichome Branching
The Calmodulin-related Calcium Sensor CML42 Plays a Role in Trichome Branching
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DOI：
10.1074/jbc.m109.056770
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发表时间：
2009-11-13
影响因子：
4.8
通讯作者：
Snedden, Wayne A.
中科院分区：
文献类型：
--
作者：
Dobney, Stephanie;Chiasson, David;Snedden, Wayne A.
钙离子（Ca 2+）是真核生物中的关键第二信使，在真核生物中，它调节响应于外部刺激的多种细胞过程。钙调素（CaM）是动物和植物中一种重要的钙离子感受器。除了进化上保守的CaM，植物还具有独特的CaM-like（CML）蛋白家族。这些CML的大多数尚未被研究，和调查其物理性质和细胞功能将提供深入了解植物中的Ca 2+信号转导。在这里，我们描述了CML 42，一个191个氨基酸的钙离子结合蛋白从拟南芥的表征。通过荧光光谱、NMR光谱、微量热法和CD光谱评估Ca 2+与重组CML 42的结合。CML 42显示出显著的α-螺旋二级结构，以30至430 nM的亲和力结合三个Ca 2+分子，并经历Ca 2+诱导的构象变化，导致一个或多个疏水区域暴露。基因表达分析揭示了CML 42转录本在不同的发展阶段和许多细胞类型，包括支持细胞，它围绕着叶表面上的毛状体（叶毛）。使用酵母双杂交筛选，我们确定了一个假定的CML 42相互作用;驱动蛋白相互作用的钙结合蛋白（KIC）。由于KIC是已知在毛状体发育中起作用的蛋白质，我们检查了转基因CML 42敲除植物，发现它们具有增加分支的异常毛状体。总的来说，我们的数据支持CML 42作为Ca 2+传感器的作用，在毛状体的细胞分支过程中发挥作用。
Calcium (Ca2+) is a key second messenger in eukaryotes where it regulates a diverse array of cellular processes in response to external stimuli. An important Ca2+ sensor in both animals and plants is calmodulin (CaM). In addition to evolutionarily conserved CaM, plants possess a unique family of CaM-like (CML) proteins. The majority of these CMLs have not yet been studied, and investigation into their physical properties and cellular functions will provide insight into Ca2+ signal transduction in plants. Here we describe the characterization of CML42, a 191-amino acid Ca2+-binding protein from Arabidopsis. Ca2+ binding to recombinant CML42 was assessed by fluorescence spectroscopy, NMR spectroscopy, microcalorimetry, and CD spectroscopy. CML42 displays significant alpha-helical secondary structure, binds three molecules of Ca2+ with affinities ranging from 30 to 430 nM, and undergoes a Ca2+-induced conformational change that results in the exposure of one or more hydrophobic regions. Gene expression analysis revealed CML42 transcripts at various stages of development and in many cell types, including the support cells, which surround trichomes (leaf hairs) on the leaf surface. Using yeast two-hybrid screening we identified a putative CML42 interactor; kinesin-interacting Ca2+-binding protein (KIC). Because KIC is a protein known to function in trichome development, we examined transgenic CML42 knockout plants and found that they possess aberrant trichomes with increased branching. Collectively, our data support a role for CML42 as a Ca2+ sensor that functions during cell branching in trichomes.