The kinetics of effector binding to phosphofructokinase. The binding of Mg2+-1,N6-ethenoadenosine triphosphate to the catalytic site.
1. The binding of the fluorescent ATP analogue, Mg2+-1,N6-etheno-ATP, to the catalytic site of rabbit skeletal muscle phosphofructokinase has been studied by stopped-flow fluorimetry [Roberts & Kellet (1979) Biochem. J. 183, 349--360]. 2. Binding of Mg2+-1,N6-etheno-ATP to the catalytic site is consistent with a two-step mechanism of the type: (formula: see text); in which the diffusion-controlled binding of ligand, L, is accompanied by prior interconversion of enzyme from one form, E, to another, E. 3. The allosteric activators, phosphate and cyclic AMP, which promote an R-type conformation, appear to stabilize slightly different conformations, R and R' respectively. 4. The binding of Mg2+-1,N6-etheno-ATP to the catalytic site is strongly affected by its binding to the inhibitory site. The rate constant for the displacement of Mg2+-1,N6-ethenol-ATP from the catalytic site, k32, is 470 +/- 35 s-1 for the R' conformation, whereas it is 6.0 +/- 0.09 s-1 for the T conformation induced by binding of Mg2+-1,N6-ethenol-ATP to the inhibitory site.
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives*; D000818:Animals; D001665:Binding Sites; D000242:Cyclic AMP; D004985:Ethenoadenosine Triphosphate / Q000378:metabolism*; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D009132:Muscles / Q000201:enzymology; D010732:Phosphofructokinase-1 / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D011817:Rabbits; D013050:Spectrometry, Fluorescence
D004985:Ethenoadenosine Triphosphate; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D010732:Phosphofructokinase-1; D008274:Magnesium