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Characterization of dual specificity protein kinase from maize seedlings.

100%
Trojanek J. B., Klimecka M. M., Fraser A., Dobrowolska G., Muszyńska G.
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vol. 51
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issue 3
635-647
EN
A protein kinase of 57 kDa, able to phosphorylate tyrosine in synthetic substrates pol(Glu4,Tyr1) and a fragment of Src tyrosine kinase, was isolated and partly purified from maize seedlings (Zea mays). The protein kinase was able to phosphorylate exogenous proteins: enolase, caseins, histones and myelin basic protein. Amino acid analysis of phosphorylated casein and enolase, as well as of phosphorylated endogenous proteins, showed that both Tyr and Ser residues were phosphorylated. Phosphotyrosine was also immunodetected in the 57 kDa protein fraction. In the protein fraction there are present 57 kDa protein kinase and enolase. This co-purification suggests that enolase can be an endogenous substrate of the kinase. The two proteins could be resolved by two-dimensional electrophoresis. Specific inhibitors of typical protein-tyrosine kinases had essentially no effect on the activity of the maize enzyme. Staurosporine, a nonspecific inhibitor of protein kinases, effectively inhibited the 57 kDa protein kinase. Also, poly L-lysine and heparin inhibited tyrosine phosphorylation by 57 kDa maize protein kinase. The substrate and inhibitor specificities of the 57 kDa maize protein kinase phosphorylating tyrosine indicate that it is a novel plant dual-specificity protein kinase.
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Regulation of wound-responsive calcium-dependent protein kinase from maize (ZmCPK11) by phosphatidic acid

86%
Klimecka M., Szczegielniak J., Godecka L., Lewandowska-Gnatowska E., Dobrowolska G., Muszyńska G.
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2011
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vol. 58
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issue 4
589-595
EN
In plant cells, phospholipids are not only membrane components but also act as second messengers interacting with various proteins and regulating diverse cellular processes, including stress signal transduction. Here, we report studies on the effects of various phospholipids on the activity and expression of maize wound-responsive calcium-dependent protein kinase (ZmCPK11). Our results revealed that in leaves treated with n-butanol, a potent inhibitor of phosphatidic acid (PA) synthesis catalyzed by phospholipase D, a significant decrease of ZmCPK11 activity was observed, indicating contribution of PA in the kinase activation. Using lipid binding assays, we demonstrate that among various phospholipids only saturated acyl species (16 : 0 and 18 : 0) of phosphatidic acid are able to bind to ZmCPK11. Saturated acyl species of PA are also able to stimulate phosphorylation of exogenous substrates by ZmCPK11 and autophosphorylation of the kinase. The level of ZmCPK11 autophosphorylation is correlated with its enzymatic activity. RT-PCR analysis showed that transcript level of ZmCPK11 in maize leaves increased in response to PA treatment. The influence of PA on the activity and transcript level of ZmCPK11 suggests an involvement of this kinase in a PA-mediated wound signal transduction pathway.
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