Coenzyme A Binding to the Aminoglycoside Acetyltransferase (3)-IIIb Increases Conformational Sampling of Antibiotic Binding Site

NMR spectroscopy experiments and molecular dynamics simulations were performed to describe the dynamic properties of the aminoglycoside acetyltransferase (3)-IIIb (AAC) in its apo and coenzyme A (CoASH) bound forms. The 15N–1H HSQC spectra indicate a partial structural change and coupling of the CoASH binding site with another region in the protein upon the CoASH titration into the apo enzyme. Molecular dynamics simulations indicate a significant structural and dynamic variation of the long loop in the antibiotic binding domain in the form of a relatively slow (250 ns), concerted opening motion in the CoASH–enzyme complex and that binding of the CoASH increases the structural flexibility of the loop, leading to an interchange between several similar equally populated conformations.