Structure of the Antibiotic Resistance Factor Spectinomycin Phosphotransferase from Legionella pneumophila |
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Authors: | Desiree H Fong Christopher T Lemke Jiyoung Hwang Bing Xiong and Albert M Berghuis |
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Institution: | From the ‡Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6 and ;the §Department of Microbiology and Immunology, McGill University, Montreal, Quebec H3A 2B4, Canada |
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Abstract: | Aminoglycoside phosphotransferases (APHs) constitute a diverse group of enzymes that are often the underlying cause of aminoglycoside resistance in the clinical setting. Several APHs have been extensively characterized, including the elucidation of the three-dimensional structure of two APH(3′) isozymes and an APH(2″) enzyme. Although many APHs are plasmid-encoded and are capable of inactivating numerous 2-deoxystreptmaine aminoglycosides with multiple regiospecificity, APH(9)-Ia, isolated from Legionella pneumophila, is an unusual enzyme among the APH family for its chromosomal origin and its specificity for a single non-2-deoxystreptamine aminoglycoside substrate, spectinomycin. We describe here the crystal structures of APH(9)-Ia in its apo form, its binary complex with the nucleotide, AMP, and its ternary complex bound with ADP and spectinomycin. The structures reveal that APH(9)-Ia adopts the bilobal protein kinase-fold, analogous to the APH(3′) and APH(2″) enzymes. However, APH(9)-Ia differs significantly from the other two types of APH enzymes in its substrate binding area and that it undergoes a conformation change upon ligand binding. Moreover, kinetic assay experiments indicate that APH(9)-Ia has stringent substrate specificity as it is unable to phosphorylate substrates of choline kinase or methylthioribose kinase despite high structural resemblance. The crystal structures of APH(9)-Ia demonstrate and expand our understanding of the diversity of the APH family, which in turn will facilitate the development of new antibiotics and inhibitors. |
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Keywords: | Antibiotics Drug Resistance/Bacteria Enzymes/Kinase Methods/X-ray Crystallography Phosphorylation/Enzymes Protein/Structure Antibiotic Resistance |
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