外源钙调素与拟南芥悬浮培养细胞结合位点的观测及其胞外效应

以拟南芥悬浮培养细胞为实验体系，借助外源荧光及同位素标记钙调素，研究结果表明外源钙调素不能被主动内吞入细胞内，而是主要以完整分子形式结合在细胞外表面；外源纯化钙调素可促进正向型质膜囊泡中的鸟苷酸三磷酸水解酶活性升高，也可引起拟南芥悬浮细胞质游离钙离子浓度的特异升高，表明外源钙调素可能通过细胞表面位点跨膜信号转换为细胞内信号，从而调节生物学活性。

Observation of Binding Sites of Exogenous Calmodulin and Its Extracellular Effect in Suspension-Cultured Arabidopsis Cell

Peptide signals play very important roles in the process of plant development, growth and defense to various stresses. Apoplast calmodulin, putative extracellular peptide signal, not only existed in extracellular space, but also had biological functions. So it is important to provide evidences for extracellular calmodulin binding sites and mechanism of signaling. In this paper, exogenous FITC-ACaM2 was observed only in the outside of cell using Laser scanning confocal microscope (Fig. 2), and (35)S-ACaM2 binding to suspension-cultured Arabidopsis cells at 25 degrees C was equal to that at 4 degrees C (Fig. 3), provided direct evidences that exogenous calmodulin was not endocytosed into cytoplasm. SDS-PAGE and radiography showed (35)S-ACaM2 intactly existed in extracellular space of suspension-cultured Arabidopsis cells (Fig. 4). Exogenous ACaM2 could specifically promote activity of GTPase(Fig. 5) and Ca(2+)](cyt) (Fig. 6). These results indicated exogenous calmodulin could bind to the surface sites of the suspension-cultured Arabidopsis cells, and then the extracellular signal was transferred into cytoplasm signal by transmembrane signaling to regulate the biological functions.