Phosphorylation/dephosphorylation of the plasma-membrane H+-ATPase (EC 3.6.1.35) could act as a regulatory mechanism to control its activity. In this work, a plasmalemma-enriched fraction from maize roots and a partially purified H+-ATPase were used to investigate the effects of Ca2+ and calmodulin on the H+-ATPase activity and on its phosphorylation status. Both the hydrolytic and the proton-pumping activities were reduced approximately 50% by micromolar Ca2+ concentrations while calmodulin did not show any effect either alone or in the presence of Ca2+. The lack of effect of calmodulin antagonists indicated that calmodulin was not involved in this response. The addition of staurosporine, a kinase inhibitor, abolished the inhibitory effect of Ca2+. Phosphorylation of plasma membrane and partially purified H+-ATPase showed the same behavior. In the presence of Ca2+ a polypeptide of 100 kDa was phosphorylated. This polypeptide cross-reacted with antibodies raised against the H+-ATPase of maize roots. The autoradiogram of the immunodetected protein clearly showed that this polypeptide, which corresponds to the H+-ATPase, was phosphorylated. Additional clear evidence comes from the immunoprecipitation experiments: the data obtained show that the H+-ATPase activity is indeed influenced by its state of phosphorylation.

Ca2+-dependent phosphorylation regulates the plasma membrane H+-ATPase activity of maize (Zea mays L.) roots / P. De Nisi, M. Dell'Orto, L. Pirovano, G. Zocchi. - In: PLANTA. - ISSN 0032-0935. - 209:2(1999 Apr), pp. 187-194.

Ca2+-dependent phosphorylation regulates the plasma membrane H+-ATPase activity of maize (Zea mays L.) roots

P. De Nisi;G. Zocchi
1999-04

Abstract

Phosphorylation/dephosphorylation of the plasma-membrane H+-ATPase (EC 3.6.1.35) could act as a regulatory mechanism to control its activity. In this work, a plasmalemma-enriched fraction from maize roots and a partially purified H+-ATPase were used to investigate the effects of Ca2+ and calmodulin on the H+-ATPase activity and on its phosphorylation status. Both the hydrolytic and the proton-pumping activities were reduced approximately 50% by micromolar Ca2+ concentrations while calmodulin did not show any effect either alone or in the presence of Ca2+. The lack of effect of calmodulin antagonists indicated that calmodulin was not involved in this response. The addition of staurosporine, a kinase inhibitor, abolished the inhibitory effect of Ca2+. Phosphorylation of plasma membrane and partially purified H+-ATPase showed the same behavior. In the presence of Ca2+ a polypeptide of 100 kDa was phosphorylated. This polypeptide cross-reacted with antibodies raised against the H+-ATPase of maize roots. The autoradiogram of the immunodetected protein clearly showed that this polypeptide, which corresponds to the H+-ATPase, was phosphorylated. Additional clear evidence comes from the immunoprecipitation experiments: the data obtained show that the H+-ATPase activity is indeed influenced by its state of phosphorylation.
H+-ATPase ; Plasma membrane ; Protein phosphorylation ; Zea
Settore AGR/13 - Chimica Agraria
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2434/240352
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