具有可插膜结构的新型钙调素类似蛋白的结构与功能研究

我们在水稻中发现一种新型的钙调素类似蛋白的基因，在它编码的187个氨基酸中，N端的149个氨基酸与不同来源移植序列的钙调素有80-90%的同源性，C末端有一个CAAL结构，此结构为可能的异戊烯化修饰位点，被修饰后的蛋白质则具有插膜或跨膜功能。本研究旨在分析测蛋白的一级和高级结构，并确定其是否具有钙调素的活性及插膜或跨膜功能。

Calmodulin (CaM) is a small heat-stable Ca2+-bindinding protein highly conserved in eukaryotes. An unusual rice calmodulin isoform, OsCaM61, was first obtained in our lab, which contains an N-terminal CaM domain and a C-terminal basic extension with a potential prenylation site. In vitro activity assays confirm OsCaM61 as a functional calmodulin. Using the green fluorescent protein (GFP) as a visual marker, we further studied subcellular localization of OsCaM61 in stably transformed tobacco cells. The GFP- OsCaM61 fusion protein was membrane-associated whereas OsCaM61-GFP was mainly detected in the nucleoplasm. GFP- OsCaM61 was transported into the nucleoplasm upon a block in isoprenoid biosynthesis by mevinolin treatment of tobacco cells. These results indicate that the prenylated OsCaM61 molecules are mainly membrane-associated while its unprenylated counterparts are transported into the nucleoplasm. Thus, OsCaM61 may play functions in coordinating Ca2+ signaling with isoprenoid metabolism. ..