Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.6.3.1 (NADPH oxidase)
 11,281 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Under drought stress, ABA promotes stomatal closure to prevent water loss. Although protein phosphorylation plays an important role in ABA signaling, little is known about these processes at the biochemical level. In this study, we searched for substrates of protein kinases in ABA signaling through the binding of a 14-3-3 protein to phosphorylated proteins using Vicia guard cell protoplasts. ABA induced binding of a 14-3-3 protein to proteins with molecular masses of 61, 43 and 39 kDa, with the most remarkable signal for the 61 kDa protein. The ABA-induced binding to the 61 kDa protein occurred only in guard cells, and reached a maximum within 3 min at 1 microM ABA. The 61 kDa protein localized in the cytosol. ABA induced the binding of endogenous vf14-3-3a to the 61 kDa protein in guard cells. Autophosphorylation of ABA-activated protein kinase (AAPK), which mediates anion channel activation, and ABA-induced phosphorylation of the 61 kDa protein showed similar time courses and similar sensitivities to the protein kinase inhibitor K-252a. AAPK elicits the binding of the 14-3-3 protein to the 61 kDa protein in vitro when AAPK in guard cells was activated by ABA. The phosphorylation of the 61 kDa protein by ABA was not affected by the NADPH oxidase inhibitor, H(2)O(2), W-7 or EGTA. From these results, we conclude that the 61 kDa protein may be a substrate for AAPK and that the 61 kDa protein is located upstream of H(2)O(2) and Ca(2+), or on Ca(2+)-independent signaling pathways in guard cells.
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PMID:Protein phosphorylation and binding of a 14-3-3 protein in Vicia guard cells in response to ABA. 1763 79

Reactive oxygen species (ROS) produced by NADPH oxidases play critical roles in signalling and development. Given the high toxicity of ROS, their production is tightly regulated. In Arabidopsis, respiratory burst oxidase homologue F (AtrbohF) encodes NADPH oxidase. Here we characterised the activation of AtRbohF using a heterologous expression system. AtRbohF exhibited ROS-producing activity that was synergistically activated by protein phosphorylation and Ca2+. The two EF-hand motifs of AtRbohF in the N-terminal cytosolic region were crucial for its Ca2+-dependent activation. AtrbohD and AtrbohF are involved in stress responses. Although the activation mechanisms for AtRbohD and AtRbohF were similar, AtRbohD had significantly greater ROS-producing activity than AtRbohF, which may reflect their functional diversity, at least in part. We further characterised the interrelationship between Ca2+ and phosphorylation regarding activation and found that protein phosphorylation-induced activation was independent of Ca2+. In contrast, K-252a, a protein kinase inhibitor, inhibited the Ca2+-dependent ROS-producing activity of AtRbohD and AtRbohF in a dose-dependent manner, suggesting that protein phosphorylation is a prerequisite for the Ca2+-dependent activation of Rboh. Positive feedback regulation of Ca2+ and ROS through AtRbohC has been proposed to play a critical role in root hair tip growth. Our findings suggest that Rboh phosphorylation is the initial trigger for the plant Ca2+-ROS signalling network.
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PMID:Protein phosphorylation is a prerequisite for the Ca2+-dependent activation of Arabidopsis NADPH oxidases and may function as a trigger for the positive feedback regulation of Ca2+ and reactive oxygen species. 2200 2