Characterization of phosphatidylinositol phosphate kinases from the moss Physcomitrella patens: PpPIPK1 and PpPIPK2.
Plant Cell Physiol
; 50(3): 595-609, 2009 Mar.
Article
em En
| MEDLINE
| ID: mdl-19188261
ABSTRACT
Phosphoinositides (PIs) play a major role in eukaryotic cells, despite being a minor component of most membranes. This is the first report on PI metabolism in a bryophyte, the moss Physcomitrella patens. Moss PI composition is similar to that of other land plants growing under normal conditions. In contrast to the large number of PIPK genes present in flowering plants, the P. patens genome encodes only two type I/II PIPK genes, PpPIPK1 and PpPIPK2, which are very similar at both the nucleotide and protein product levels. However, the expression of the two genes is differentially regulated, and in vitro biochemical characterization shows that the resulting enzymes have different substrate specificities. PpPIPK1 uses PtdIns4P and PtdIns3P with similar preference and also metabolizes PtdIns(3,4)P(2) to produce PtdIns(3,4,5)P(3), a PI not yet detected in intact plant cells. PpPIPK2 prefers PtdIns as substrate and is much less active towards PtdIns4P and PtdIns3P. Thus, PpPIPK2 shows properties reminiscent of both PtdInsP-kinase and PtdIns-kinases. Moreover, a substitution of glutamic acid by alanine in the activation loop drastically reduced PpPIPK1 activity and altered the substrate specificity to PtdIns5P being the preferred substrate compared with PtdIns4P and PtdIns3P. These findings demonstrate that the substrate specificity of plant PIPKs is determined in a plant-specific manner, which provides new insights into the regulatory modes of PIPK activity in plants.
Texto completo:
1
Bases de dados:
MEDLINE
Assunto principal:
Fosfotransferases (Aceptor do Grupo Álcool)
/
Bryopsida
Idioma:
En
Revista:
Plant Cell Physiol
Assunto da revista:
BOTANICA
Ano de publicação:
2009
Tipo de documento:
Article
País de afiliação:
Suécia