Equilibrium binding of thioredoxin fB to chloroplastic fructose bisphosphatase. Evidence for a thioredoxin site distinct from the active site.
Thioredoxin fB, the protein activator of chloroplastic fructose 1,6-bisphosphatase, strongly binds its target enzyme with a stoichiometry of one protein dimer per enzyme tetramer. The thioredoxin binding site is distinct from the active site and the dissociation constant of the protein-enzyme complex has the extremely small value of 769 nM at pH 7.5. This interaction involves both ionic and hydrophobic contributions and is enhanced by a pH increase from 7 to 8. These results suggest that the above molecular properties may be involved in the light activation of chloroplastic fructose bisphosphatase.
D001665:Binding Sites; D054479:Chloroplast Thioredoxins; D002736:Chloroplasts / Q000201:enzymology*; D004789:Enzyme Activation / Q000528:radiation effects; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008027:Light; D009282:Naphthalenesulfonates; D009994:Osmolar Concentration; D010940:Plant Proteins / Q000378:metabolism*; D010944:Plants / Q000201:enzymology; D011485:Protein Binding; D013816:Thermodynamics; D013879:Thioredoxins
D054479:Chloroplast Thioredoxins; D009282:Naphthalenesulfonates; D010940:Plant Proteins; D013879:Thioredoxins; C009497:2-(4-toluidino)-6-naphthalenesulfonic acid; D006597:Fructose-Bisphosphatase