Kinetics and molecular modelling of ligand binding to ribulose 1, 5‐bisphosphate carboxylase/oxygenase (RUBISCO)

Abstract

AbstractThe dye 2‐toluidinonaphthalino‐6‐sulphonate TNS is sensitive to ligand binding events at the active site of RUBISCO purified from spinach or Rhodospirillum rubrum. Equilibrium binding curves of the substrate D‐ribulose 1, 5‐bisphosphate RUBP and the inhibitor 6‐D‐phosphogluconate 6‐PG to RUBISCO from spinach were apparently biphasic. Iodine laser temperature jump (ILTJ) experiments showed a fast and a slow bimolecular binding reaction of both ligands corresponding to a strong and a weak equilibrium binding process. In Stopped Flow (SF) experiments different reaction mechanisms were observed for the binding of the transition state analogue 2‐carboxy‐D‐arabinitol 1, 5‐bisphosphate CABP to RUBISCO in the presence and absence of magnesium ions. In the absence of magnesium ions CABP binds in a reversible bimolecular binding reaction to RUBISCO. In the presence of magnesium ions an irreversible two step reaction mechanism for the CABP binding was detected. Molecular dynamic (MD) simulations of ligand binding to RUBISCO were used for modelling of the strong influence of magnesium ions on the kinetics of ligand binding to RUBISCO.