Biochemical properties and physiological role of novel proteins involved in regulation of phosphatidylinositol phosphates.

拟南芥质膜相关钙结合蛋白(PCAPS)是一种新型蛋白，它与钙调素(CaM)/钙复合体和磷脂酰肌醇磷酸盐(PIPs)在N端结合。PCAP是肉豆蔻酰化的，并稳定地与质膜结合。PCAPS在细胞静息状态与PIP结合，当胞浆内钙离子水平升高时，结合CaM/Ca。因此，推测PCAPS在钙信号转导到PIP信号转导中具有重要作用。在本研究中，我们证明了PCaP1参与了叶片气孔的关闭，PCaP2通过处理质膜上的Ca~(2+)和PtdInsP信号来调节根毛尖端的生长。

Plasma membrane-associated Ca2+-binding proteins (PCaPs) of Arabidopsis thaliana is a novel-type proteins that bind to the calmodulin (CaM)/Ca complex and phosphatidylinositol phosphates (PIPs) at their N-terminal parts. PCaPs are myristoylated and stably associated with the plasma membrane. PCaPs bind PIPs at resting state of cells and CaM/Ca when the cytoplasolic Ca2+level is increased. Thus, it is estimated that PCaPs function as transducers from Ca-signaling to PIP-signaling. During the present study, we demonstrated that PCaP1 is involved in closure of stomata in leaves and that PCaP2 regulates root hair tip growth via processing Ca2+and PtdInsP signals on the plasma membrane.