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| Title: Regulation of MAP kinase phosphatase 1 ( AtMKP1 ) by calmodulin in Arabidopsis .
| | Author: Lee K Song EH Kim HS Yoo JH Han HJ Jung MS Lee SM Kim KE Kim MC Cho MJ Chung WS | | Journal: J Biol Chem Citation: V : P : Year: 2008 Type: Publisher | | Literature: oryza Field: abstract Doc ID: pub18579522 Accession (PMID): 18579522 | | Abstract: The mitogen-activated protein kinases ( MAPKs ) are key signal transduction molecules , which respond to various external stimuli .
The MAPK phosphatases ( MKPs ) are known to be negative regulators of MAPKs in eukaryotes .
We screened an Arabidopsis cDNA library using horseradish peroxidase-conjugated calmodulin ( CaM ) , and isolated AtMKP1 as a CaM-binding protein .
Recently , tobacco NtMKP1 and rice OsMKP1 , two orthologs of Arabidopsis AtMKP1 , were reported to bind CaM via a single putative CaM binding domain ( CaMBD ) .
However , little is known about the regulation of phosphatase activity of plant MKP1s by CaM binding .
In this study , we identified two Ca2+-dependent CaMBDs within AtMKP1 .
Specific binding of CaM to two different CaMBDs was verified using a gel mobility shift assay , a competition assay with a Ca2+/CaM-dependent enzyme and a split-ubiquitin assay .
The peptides for two CaMBDs , CaMBDI and CaMBDII , bound CaM in a Ca2+-dependent manner , and the binding affinity of CaMBDII was found to be higher than that of CaMBDI .
CaM overlay assays using mutated CaMBDs showed that four amino acids , Trp453 and Leu456 in CaMBDI and Trp678 and Ile684 in CaMBDII , play a pivotal role in CaM binding .
Moreover , the phosphatase activity of AtMKP1 was increased by CaM in a Ca2+-dependent manner .
Our results suggest that two important signaling pathways , Ca2+ signaling and the MAPK signaling cascade , are connected in plants via the regulation of AtMKP1 activity .
To our knowledge , this is the first report to show that the biochemical activity of MKP1 in plants is regulated by CaM .
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[ Sen. 5, subscore: 1.00 ]: However , little is known about the regulation of phosphatase activity of plant MKP1s by CaM binding .
[ Sen. 12, subscore: 1.00 ]: To our knowledge , this is the first report to show that the biochemical activity of MKP1 in plants is regulated by CaM .
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