Relationship between chiroptical properties, structural changes and interactions in enzymes: a computational study on beta-lactamases from class A

Enzyme functions such as catalysis, binding and regulation are directly related to a variety of conformational changes. A sensitive and useful method for their investigation is circular dichroism (CD) and a rotational strength (R) is its fundamental characteristic. In this study, we show how the sensitivity of the mechanisms of rotational strengths to important conformational changes depends on the chromophore environment in two beta-lactamases from class A (from Escherichia coli and B. licheniformis). Rotational strengths have been calculated using the matrix method and including the effects of local environment (LE). X-ray structures (of protein components) of several enzyme-ligand complexes from the catalytic cycle of the TEM-1 enzyme and for both crystallographic monomers of the enzyme from B. licheniformis were used. An analysis of the relative degree of perturbation of the rotational strengths upon local interactions is performed.