Abstract
Phosphatidylinositol 5-kinase (PIPK) regulates vesicle trafficking and cytoskeletal organization via phospharylation of phosphatidylinositol-monophosphates in animals and yeasts. However, the activation mode and function of PIPKs in plants are largely unknown. We analyzed plasma membrane-localization and activation of PIPKs from Physcomitrella patens (PpPIPKs). Plant PIPKs consist of N-terminal MORN and C-terminal catalytic domains and the former is thought to be responsible for plasma membrane-localization. In contrast, the catalytic domain is important for membrane localization for animal PIPKs. When the catalytic domain of PpPIPKs was fused to GFP, plasma membrane-localization was observed, although a MORN-GFP fusion located in cytoplasm. Thus, the MORM domain is not involved in membrane localization in Physcomitrella. Moreover, amino acids regulating membrane localization and enzymatic activity were identified in the activation loop as is in animal PIPKs. We therefore concluded that the machineries regulating plasma membrane-localization and enzymatic activity of PIPKs are conserved in eukaryotes.
