Abstract
ADP-glucose pyrophosphorylase (AGPase) catalyzes the first committed step of starch synthesis in plants. The potato tuber enzyme contains a pair of catalytic small subunits (SSs) and a pair of non-catalytic large subunits (LSs). We have previously identified a LS mutant containing a P52L replacement, which rendered the enzyme with down-regulatory properties. To investigate the structure-function relationships between the two subunits with regard to allosteric regulation, putative SS mutants that could reverse the down-regulatory condition of LS(P52L) were identified by their ability to restore glycogen accumulation in an AGPase-deficient Escherichia coli glgC-strain. Two distinct LS-dependent classes, bona fide SS suppressors dependent on LS(P52L) but not LS(WT) and SS up-regulating allosteric mutants, were evident by kinetic analysis. These results indicate that both LS and SS have a regulatory function in controlling allosteric properties through enhancing cooperative subunit interactions.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
MeSH terms
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Adenosine Diphosphate Glucose / metabolism
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Adenosine Triphosphate / chemistry
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Adenosine Triphosphate / metabolism
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Adenosine Triphosphate / pharmacology
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Allosteric Regulation
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Amino Acid Substitution
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Binding Sites / genetics
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Catalysis / drug effects
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Escherichia coli / genetics
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Glucose-1-Phosphate Adenylyltransferase / chemistry*
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Glucose-1-Phosphate Adenylyltransferase / genetics
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Glucose-1-Phosphate Adenylyltransferase / metabolism*
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Glyceric Acids / chemistry
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Glyceric Acids / metabolism
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Glyceric Acids / pharmacology
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Kinetics
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Models, Molecular
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Mutant Proteins / chemistry
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Mutant Proteins / genetics
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Mutant Proteins / metabolism
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Mutation
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Plant Tubers / enzymology*
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Plant Tubers / genetics
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Protein Structure, Tertiary
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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 / isolation & purification
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Recombinant Proteins / metabolism
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Solanum tuberosum / enzymology*
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Solanum tuberosum / genetics
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Structure-Activity Relationship
Substances
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Glyceric Acids
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Mutant Proteins
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Protein Subunits
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Recombinant Proteins
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Adenosine Diphosphate Glucose
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3-phosphoglycerate
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Adenosine Triphosphate
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Glucose-1-Phosphate Adenylyltransferase