LAUSR

&NA; The molecular recognition and interaction of beta‐lactamase II from Bacillus cereus (Bc II) with penicillin V (PV) and sulbactam (Sul) especially conformational changes of Bc II in the binding process were studied through spectroscopy analysis in combination with molecular dynamics (MD) simulation. The results show that in the binding process, a new coordination bond is observed between the Zn2 of Bc II and the carboxyl‐O of PV or Sul by replacing His204. Electrostatic interaction between Zn2 and the ligand provide main driving force for the binding affinity. Compared with apo Bc II, there are mainly four loops showing significant conformational changes in ligand‐bound Bc II. A weak conformational transformation from &bgr;‐sheets to random coils is observed in the loop2 of ligand‐bound Bc II. The conformational transformation may depend on the functional group and binding pose of the ligand, giving the binding pocket greater flexibility and accordingly allowing for an induced fit of the enzyme‐ligand binding site around the newly introduced ligand. The change in the loop2 of ligand‐bound Bc II may lead to the opening of the binding pocket of Bc II. Therefore, loop2 can be considered a gate for control of ligand access in Bc II, hence its dynamic response should be considered in new drug design and development. HighlightsThe molecular recognition and interaction of Bc II with PV and Sul were studied.Results from fluorescence, CD and MD simulations were compared and discussed.A conformational transformation from &bgr;‐sheets to random coils was observed in Bc II.