Cloning and characterization of a novel radish protein kinase which is homologous to fungal cot-I like and animal Ndr protein kinases.
According to the similarity of the amino acid sequences in their catalytic domains, eukaryotic protein kinases have been classified into the five main groups: 'AGC', 'CaMK', 'CMGC', 'PTK' and 'other'. The AGC group, represented by the cyclic nucleotide-dependent kinases (PKA and PKG), the calcium-phospholipid-dependent kinases (PKC) and the ribosomal S6 protein kinases, are poorly characterized in plants except for a few cases. In this study, in order to gain a better understanding of plant protein kinases in the AGC group, three cDNAs encoding novel protein kinases, RsNdr1 and RsNdr2a/b, were cloned from radish and characterized by molecular and biochemical methods. The deduced amino acid sequences of RsNdr1 and RsNdr2a/b contained all 12 conserved catalytic subdomains which are characteristic of the eukaryotic Ser/Thr protein kinases. A cell lysate from E. coli overexpressing RsNdr1 fusion protein had protein kinase activity toward a conventional protein substrate (myelin basic protein), whereas that from E. coli harboring a fusion plasmid encoding kinase-dead RsNdr1 or RsNdr2 did not show any protein kinase activity. A phylogenetic tree for 17 protein kinases from various organisms showed that the RsNdrs are more closely related to the protein kinases in a particular subgroup of the 'AGC' (fungal cot1-like and animal Ndr kinases) than to the authentic 'AGC' protein kinases, such as PKA, PKC or ribosomal S6 kinase.
Imai
Takehiro
T
Department of Biotechnology, Faculty of Engineering, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555, Japan.
Shimamura
Satoshi
S
Kurosaka
Akira
A
Yamagishi
Hiroshi
H
Terachi
Toru
T
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D020134:Catalytic Domain / Q000235:genetics; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000032:analysis; D018744:DNA, Plant / Q000032:analysis; D004926:Escherichia coli / Q000201:enzymology; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D031224:Raphanus / Q000201:enzymology* / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction
D018076:DNA, Complementary; D018744:DNA, Plant; D012333:RNA, Messenger; D017346:Protein Serine-Threonine Kinases