A conformational transition involved in antagonistic substrate binding to the allosteric phosphofructokinase from Escherichia coli.

摘要: The binding of fructose 6-phosphate, ATP or its nonhydrolyzable analogue adenylyl 5'-(beta,gamma-methylenediphosphonate), ADP, and phosphoenolpyruvate to Escherichia coli phosphofructokinase has been studied by changes in the protein fluorescence and/or equilibrium dialysis. results lead following conclusions: (1) tetrameric can bind four but only two fructose-6-phosphate, this occurs without cooperativity; (2) conformational states, T R, with respectively a high low fluorescence, seem accessible phosphofructokinase, which exists as mixture one-third R two-third states absence ligand; (3) substrate 6-phosphate allosteric activator ADP preferentially low-fluorescence state, while other substrate, [or 5'-(beta,gamma-methylenediphosphonate)], inhibitor high-fluorescence state; (4) given ligand is cooperative, Hill coefficient 2, when accompanied complete shift from one state other; for instance, 5'-(beta,gamma-methylenediphosphonate) cooperative presence favors state. This behavior qualitatively consistent concerted transition, quite different that described earlier steady-state activity measurements (Blangy et al., 1968). discrepancy suggests properties are due part kinetics enzymatic reaction.