Fig. 1. Crystal structures of APH(3′)-IIIa in complex with ADP and kanamycin A or neomycin B. Ribbon representation of the APH(3′)-IIIa ternary complexes showing the location of the antibiotic binding site. Kanamycin (red) and neomycin (blue) are superimposed in the binding site. Magnesium ions are shown in green. Since the protein structure does not differ significantly between the two ternary complexes, only one is shown.