title: Substrate promiscuity of an aminoglycoside antibiotic resistance enzyme via target mimicry.
abstract: The misuse of antibiotics has selected for bacteria that have evolved mechanisms for evading the effects of these drugs. For aminoglycosides, a group of clinically important bactericidal antibiotics that target the A-site of the 16S ribosomal RNA, the most common mode of resistance is enzyme-catalyzed chemical modification of the drug. While aminoglycosides are structurally diverse, a single enzyme can confer resistance to many of these antibiotics. For example, the aminoglycoside kinase APH(3')-IIIa, produced by pathogenic Gram-positive bacteria such as enterococci and staphylococci, is capable of detoxifying at least 10 distinct aminoglycosides. Here we describe the crystal structures of APH(3')-IIIa in complex with ADP and kanamycin A or neomycin B. These structures reveal that the basis for this enzyme's substrate promiscuity is the presence of two alternative subsites in the antibiotic binding pocket. Furthermore, comparison between the A-site of the bacterial ribosome and APH(3')-IIIa shows that mimicry is the second major factor in dictating the substrate spectrum of APH(3')-IIIa. These results suggest a potential strategy for drug design aimed at circumventing antibiotic resistance.
authors: Department of Biochemistry, McGill University, 3775 University Street, Montreal, Quebec H3A 2B4, Canada.
authors: Desiree H
authors: DH
authors: Fong
authors: Albert M
authors: AM
authors: Berghuis
mesh_terms: D018360:Crystallography, X-Ray; D006094:Gram-Positive Bacteria / Q000201:enzymology / Q000235:genetics; D019868:Kanamycin Kinase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D013379:Substrate Specificity
chemical_list: D012336:RNA, Ribosomal, 16S; D019868:Kanamycin Kinase