Abstract
Phosphoenolpyruvate carboxylase (PEPC) is a tightly controlled anaplerotic enzyme situated at a pivotal branch point of plant carbohydrate-metabolism. In developing castor oil seeds (COS) a novel allosterically-densensitized 910-kDa Class-2 PEPC hetero-octameric complex arises from a tight interaction between 107-kDa plant-type PEPC and 118-kDa bacterial-type PEPC (BTPC) subunits. Mass spectrometry and immunoblotting with anti-phosphoSer451 specific antibodies established that COS BTPC is in vivo phosphorylated at Ser451, a highly conserved target residue that occurs within an intrinsically disordered region. This phosphorylation was enhanced during COS development or in response to depodding. Kinetic characterization of a phosphomimetic (S451D) mutant indicated that Ser451 phosphorylation inhibits the catalytic activity of BTPC subunits within the Class-2 PEPC complex.
Copyright © 2012 Federation of European Biochemical Societies. All rights reserved.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Sequence
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Amino Acid Substitution
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Antibodies, Phospho-Specific
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Castor Oil / chemistry
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Food Handling
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Isoenzymes / chemistry
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Isoenzymes / genetics
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Isoenzymes / metabolism
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Kinetics
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Molecular Sequence Data
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Mutagenesis, Site-Directed
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Mutant Proteins / chemistry
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Mutant Proteins / metabolism
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Phosphoenolpyruvate Carboxylase / chemistry
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Phosphoenolpyruvate Carboxylase / genetics
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Phosphoenolpyruvate Carboxylase / metabolism*
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Phosphorylation
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Plant Proteins / chemistry
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Plant Proteins / genetics
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Plant Proteins / metabolism*
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Protein Processing, Post-Translational
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Protein Subunits / chemistry
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Protein Subunits / genetics
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Protein Subunits / metabolism
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Recombinant Proteins / chemistry
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Recombinant Proteins / metabolism
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Ricinus / enzymology*
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Ricinus / genetics
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Ricinus / growth & development
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Seeds / enzymology*
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Seeds / growth & development
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Sequence Alignment
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Serine / metabolism*
Substances
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Antibodies, Phospho-Specific
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Isoenzymes
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Mutant Proteins
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Plant Proteins
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Protein Subunits
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Recombinant Proteins
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Serine
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Castor Oil
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Phosphoenolpyruvate Carboxylase