Protein phosphorylation by cellular networks including plant MAP-kinase cascades

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Machida : Protein kinase NPK1 that was identified in tobacco is homolohous in terms of an amino acid sequence to members of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, and NPK1 cDNA can complement a mutation of BCK1 gene, one of the yeast homologue of MAPKKK.In the present study, a cDNA for an activator of NPK1 was isolated by using an activatioin cloning system with yeast cells. Structural and immunological analyzes with the cDNA showed that it codes for a new member of a kinesin-like protein because the predicted protein has an amino acid sequence at the amino terminus that is highly homologous to that of the motor domain of the kinesin super family. The predicted protein was designated NPK1-activating kinesisn-like protein (NACK). When both NPK1 and NACK cDNAs were overexpressed in yease cells, activity of NPK1 increased by approximately 10-fold by the interaction of the carboxy-terminal region of NPK1 with the middle of the stalk region of NACK.NACK was accu … More mulated only at the M phase of the cell cycle, and NPK1 was detected from the S phase to the end of M phase. These results suggest that NPK1 can be activated at the M phase and function in a process of that phase. Shinozaki : cDNAs for nine homologues of MAP kinases, cDNAs for three homologues of MAPKK,cDNAs for four homologues of MAPKKK,cDNAs for two homologues of S6 protein kinase were cloned. Genes for some of the protein kinases (ATMPK3, ATMEKK,ATPK19) were shown to be expressed in response to drought, cold temperature and salt stress, suggesting that they constitute a single signal cascade. Oka : The results of experiments with transgenic Arabidopsis plants that have its homologue of PP1 (protein phosphatase 1) suggest that the homologue functions in positive response to ethylene. Nakamura : A 54-kDa protein kinase in tobacco leaves was activated by the treatment with sucrose, and it was shown to be a member of the CDPK family. Izui : PEP carboxylase of maize was shown to be phosphorylated by a member of CDPK.Complementary DNAs for candidate protein kiases that may be involved in such phosphorylation were cloned. Less