Subunit interactions specify the allosteric regulatory properties of the potato tuber ADP-glucose pyrophosphorylase.
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.
Kim
Dongwook
D
Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
Hwang
Seon-Kap
SK
Okita
Thomas W
TW
D000245:Adenosine Diphosphate Glucose / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D000494:Allosteric Regulation; D019943:Amino Acid Substitution; D001665:Binding Sites / Q000235:genetics; D002384:Catalysis / Q000187:drug effects; D004926:Escherichia coli / Q000235:genetics; D051599:Glucose-1-Phosphate Adenylyltransferase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005988:Glyceric Acids / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D007700:Kinetics; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D035281:Plant Tubers / Q000201:enzymology* / Q000235:genetics; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D011198:Solanum tuberosum / Q000201:enzymology* / Q000235:genetics; D013329:Structure-Activity Relationship
D005988:Glyceric Acids; D050505:Mutant Proteins; D021122:Protein Subunits; D011994:Recombinant Proteins; D000245:Adenosine Diphosphate Glucose; C005156:3-phosphoglycerate; D000255:Adenosine Triphosphate; D051599:Glucose-1-Phosphate Adenylyltransferase