Backbone resonance assignments of a promiscuous aminoglycoside antibiotic resistance enzyme; the aminoglycoside phosphotransferase(3')-IIIa.

The aminoglycoside phosphotransferase(3')-IIIa (APH) is a promiscuous enzyme and renders a large number of structurally diverse aminoglycoside antibiotics useless against infectious bacteria. A remarkable property of this approximately 31 kDa enzyme is in its unusual dynamic behavior in solution; the apo-form of the enzyme exchanges all of its backbone amide protons within 15 h of exposure to D ( 2 ) O while aminoglycoside-bound forms retain approximately 40% of the amide protons even after >90 h of exposure. Moreover, the number of observable peaks and their dispersion in HSQC spectra varies with each aminoglycoside, rendering the resonance assignments very challenging. Therefore, the binary APH-tobramycin complex, which shows the largest number of well-resolved peaks, was used for the backbone resonance assignments (Calpha, C, N, H, and some Cbeta) of this protein (BMRB-16337).