title: [Observation of binding sites of exogenous calmodulin and its extracellular effect in suspension-cultured Arabidopsis cell].
abstract: 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.
authors.affiliation: Laboratory of Molecular and Cell Biology, Hebei Normal University, Shijiazhuang 050016, China. cuisujuan@263.net
authors.forename: Su-Juan
authors.initials: SJ
authors.lastname: Cui
authors.forename: Fang
authors.initials: F
authors.lastname: Chang
authors.forename: Ying-Jie
authors.initials: YJ
authors.lastname: Gao
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Wang
authors.forename: Da-Ye
authors.initials: DY
authors.lastname: Sun
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism / Q000494:pharmacology*; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation / Q000187:drug effects; D020558:GTP Phosphohydrolases / Q000378:metabolism; D018613:Microscopy, Confocal; D015398:Signal Transduction / Q000187:drug effects; D013696:Temperature
chemical_list: D029681:Arabidopsis Proteins; D002147:Calmodulin; D020558:GTP Phosphohydrolases; D002118:Calcium