Cloning of the cDNA Encoding Plant Calcium-Dependent Protein Kinase

大豆钙依赖蛋白激酶(CDPK)是第一个从植物中提纯到均一的钙依赖蛋白激酶。这种酶代表了一类新的蛋白激酶，它们的活性依赖于微摩尔钙，但不需要磷脂或钙调蛋白来活性。初步的免疫细胞化学定位表明，CDPK与大豆和洋葱根尖细胞中的肌动蛋白细丝有关。这种联系表明，CDPK可能在植物肌动蛋白的调节中发挥作用。CDPK的纯化和鉴定使得研究钙和蛋白质磷酸化在植物中的作用成为可能。本研究通过(1)充分表征CDPK的钙结合特性，(2)确定CDPK的免疫学特性，(3)确定CDPK如何与肌动蛋白结合，以及(4)鉴定作为CDPK底物的肌动蛋白相关蛋白。植物和动物中的许多代谢活动都受到磷酸化/去磷酸化机制的调节。蛋白激酶在这种类型的调节中起着主要作用。最近，一类新的与钙离子直接结合的蛋白激酶被发现。这里定义的实验将为研究这些钙依赖蛋白激酶在调节植物细胞骨架中的潜在作用提供依据，并更好地确定其在调节植物细胞功能和植物生长发育中的作用。

Soybean calcium-dependent protein kinase (CDPK) is the first Ca2+-dependent protein kinase from plants to be purified to homogeneity. This enzyme represents a new class of protein kinases that are dependent on micromolar calcium for activity but do not require phospholipids or calmodulin for activity. Preliminary immunocytochemical localization of the enzyme shows that CDPK is associated with actin filaments in soybean and onion root tip cells. This association suggests that CDPK may play a role in the regulation of plant actin. The purification and characterization of CDPK allows the study of both the role of calcium and protein phosphorylation in plants. This research investigates these roles by (1) fully characterizing the calcium-binding properties of CDPK, (2) determining the immunological properties of CDPK, (3) determining how CDPK binds to actin, and (4) identifying actin-associated proteins that are substrates of CDPK.%%% Many metabolic activities in plants and animals are regulated by phosphorylation/dephosphorylation mechanisms. Protein kinases play a major role in this type of regulation. Recently, a new class of protein kinases which directly bind calcium have been discovered. The experiments defined here will provide for investigation of the potential role of these calcium-dependent protein kinases in the regulation of the plant cytoskeleton and to better define its role in the regulation of plant cell function and in plant growth and development.***//