Characterisation of a plant 3-phosphoinositide-dependent protein kinase-1 homologue which contains a pleckstrin homology domain

A plant homologue of mammalian 3-phosphoinositide-dependent protein kinase- 1 (PDK1) has been identified in Arabinopsis and rice which displays 40% ove rall identity with human 3-phosphoinositide-dependent protein kinase-1. Lik e the mammalian 3-phosphoinositide-dependent protein kinase-1, Arabidopsis 3-phosphoinositide-dependent protein kinase-1 and rice 3-phosphoinositide-d ependent protein kinase-1 possess a kinase domain at N-termini and a plecks trin homology domain at their C-termini, Arabidopsis 3-phosphoinositide-dep endent protein kinase-1 can rescue lethality in Saccharomyces cerevisiae ca used by disruption of the genes encoding yeast 3-phosphoinositide-dependent protein kinase-1 homologues, Arabidopsis 3-phosphoinositide-dependent prot ein kinase-1 interacts,ia its pleckstrin homology domain with phosphatidic acid, PtdIns3P, PtdIns(3,4,5)P-3 and PtdIns(3,4)P-2 and to a lesser extent with PtdIns(4,5)P-2 and PtdIns4P. Arabidopsis 3-phosphoinositide-dependent protein kinase-1 is able to activate human protein kinase B alpha (PKB/AKT) in the presence of PtdIns(3,4,5)P-3. Arabidopsis 3-phosphoinositide-depend ent protein kinase-1 is only the second plant protein reported to possess a pleckstrin homology domain and the first plant protein shown to bind 3-pho sphoinositides. (C) 1999 Federation of European Biochemical Societies.