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Oxygen deprivation stimulates Ca 2+ ‐mediated phosphorylation of mRNA cap‐binding protein eIF4E in maize roots
Author(s) -
Manjunath Sivalinganna,
Williams Alan J.,
BaileySerres Julia
Publication year - 1999
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1999.00489.x
Subject(s) - eif4e , phosphoprotein , messenger rna , protein biosynthesis , isoelectric point , phosphorylation , biology , biochemistry , binding protein , translation (biology) , microbiology and biotechnology , enzyme , gene
Summary Flooding of maize seedlings causes O 2 deprivation that leads to a global reduction in protein synthesis and selective translation of cytoplasmic mRNAs. Since selective translation in animal cells can involve the cap‐binding protein eIF4E, we characterized the distinct mRNA cap‐binding proteins eIF4E and eIFiso4E of maize. These proteins have 45% deduced amino acid sequence identity and are highly conserved at residues of eIF4E that function in intermolecular interactions in animals. Maize eIF4E is a phosphoprotein. O 2 deprivation resulted in a decrease in the isoelectric point of eIF4E, consistent with additional phosphorylation. Modification of eIF4E was mimicked by treatment with caffeine under aerobic conditions and blocked by treatment with ruthenium red under O 2 deprivation, implicating Ca 2+ as a second messenger in eIF4E modification. In contrast, no isoelectric variants of eIFiso4E were detected. The possible role of cytosolic Ca 2+ and pH in regulation of mRNA cap‐binding protein activity under O 2 deprivation is discussed.