title: A dibasic amino acid pair conserved in the activation loop directs plasma membrane localization and is necessary for activity of plant type I/II phosphatidylinositol phosphate kinase.
abstract: Phosphatidylinositol phosphate kinase (PIPK) is an enzyme involved in the regulation of cellular levels of phosphoinositides involved in various physiological processes, such as cytoskeletal organization, ion channel activation, and vesicle trafficking. In animals, research has focused on the modes of activation and function of PIPKs, providing an understanding of the importance of plasma membrane localization. However, it still remains unclear how this issue is regulated in plant PIPKs. Here, we demonstrate that the carboxyl-terminal catalytic domain, which contains the activation loop, is sufficient for plasma membrane localization of PpPIPK1, a type I/II B PIPK from the moss Physcomitrella patens. The importance of the carboxyl-terminal catalytic domain for plasma membrane localization was confirmed with Arabidopsis (Arabidopsis thaliana) AtPIP5K1. Our findings, in which substitution of a conserved dibasic amino acid pair in the activation loop of PpPIPK1 completely prevented plasma membrane targeting and abolished enzymatic activity, demonstrate its critical role in these processes. Placing our results in the context of studies of eukaryotic PIPKs led us to conclude that the function of the dibasic amino acid pair in the activation loop in type I/II PIPKs is plant specific.
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, Hakodate 041-8611, Japan. komikami@fish.hokudai.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Mikami
authors.forename: Laura
authors.initials: L
authors.lastname: Saavedra
authors.forename: Yuji
authors.initials: Y
authors.lastname: Hiwatashi
authors.forename: Toshiki
authors.initials: T
authors.lastname: Uji
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Hasebe
authors.forename: Marianne
authors.initials: M
authors.lastname: Sommarin
mesh_terms: D000595:Amino Acid Sequence; D000599:Amino Acids, Diamino / Q000737:chemistry*; D000818:Animals; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D019068:Bryopsida / Q000187:drug effects / Q000201:enzymology*; D020134:Catalytic Domain; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology*; D017124:Conserved Sequence; D004789:Enzyme Activation / Q000187:drug effects; D008969:Molecular Sequence Data; D019697:Onions / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D010712:Phosphatidic Acids / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry* / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D011523:Protoplasts / Q000187:drug effects / Q000201:enzymology; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology
chemical_list: D000599:Amino Acids, Diamino; D010712:Phosphatidic Acids; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase