Nucleotide selectivity of antibiotic kinases.
Antibiotic kinases, which include aminoglycoside and macrolide phosphotransferases (APHs and MPHs), pose a serious threat to currently used antimicrobial therapies. These enzymes show structural and functional homology with Ser/Thr/Tyr kinases, which is suggestive of a common ancestor. Surprisingly, recent in vitro studies using purified antibiotic kinase enzymes have revealed that a number are able to utilize GTP as the antibiotic phospho donor, either preferentially or exclusively compared to ATP, the canonical phosphate donor in most biochemical reactions. To further explore this phenomenon, we examined three enzymes, APH(3')-IIIa, APH(2'')-Ib, and MPH(2')-I, using a competitive assay that mimics in vivo nucleotide triphosphate (NTP) concentrations and usage by each enzyme. Downstream analysis of reaction products by high-performance liquid chromatography enabled the determination of partitioning of phosphate flux from NTP donors to antibiotics. Using this ratio along with support from kinetic analysis and inhibitor studies, we find that under physiologic concentrations of NTPs, APH(3')-IIIa exclusively uses ATP, MPH(2')-I exclusively uses GTP, and APH(2'')-Ib is able to use both species with a preference for GTP. These differences reveal likely different pathways in antibiotic resistance enzyme evolution and can be exploited in selective inhibitor design to counteract resistance.
M G DeGroote Institute for Infectious Disease Research, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.
Tushar
T
Shakya
Gerard D
GD
Wright
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D001667:Binding, Competitive / Q000502:physiology; D024881:Drug Resistance, Bacterial / Q000502:physiology; D006160:Guanosine Triphosphate / Q000378:metabolism; D019868:Kanamycin Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008956:Models, Chemical; D009711:Nucleotides / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
D000900:Anti-Bacterial Agents; D009711:Nucleotides; D006160:Guanosine Triphosphate; D017853:Phosphotransferases (Alcohol Group Acceptor); C048564:aminoglycoside 2''-phosphotransferase; C061369:macrolide 2'-kinase; D019868:Kanamycin Kinase; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases