title: Identification and characterization of an allosteric inhibitory site on dihydropteroate synthase.
abstract: The declining effectiveness of current antibiotics due to the emergence of resistant bacterial strains dictates a pressing need for novel classes of antimicrobial therapies, preferably against molecular sites other than those in which resistance mutations have developed. Dihydropteroate synthase (DHPS) catalyzes a crucial step in the bacterial pathway of folic acid synthesis, a pathway that is absent in higher vertebrates. As the target of the sulfonamide class of drugs that were highly effective until resistance mutations arose, DHPS is known to be a valuable bacterial Achilles heel that is being further exploited for antibiotic development. Here, we report the discovery of the first known allosteric inhibitor of DHPS. NMR and crystallographic studies reveal that it engages a previously unknown binding site at the dimer interface. Kinetic data show that this inhibitor does not prevent substrate binding but rather exerts its effect at a later step in the catalytic cycle. Molecular dynamics simulations and quasi-harmonic analyses suggest that the effect of inhibitor binding is transmitted from the dimer interface to the active-site loops that are known to assume an obligatory ordered substructure during catalysis. Together with the kinetics results, these structural and dynamics data suggest an inhibitory mechanism in which binding at the dimer interface impacts loop movements that are required for product release. Our results potentially provide a novel target site for the development of new antibiotics.
authors.affiliation: Departments of †Structural Biology and ‡Chemical Biology and Therapeutics, St. Jude Children's Research Hospital , Memphis, Tennessee 38105, United States.
authors.forename: Dalia I
authors.initials: DI
authors.lastname: Hammoudeh
authors.forename: Mihir
authors.initials: M
authors.lastname: Daté
authors.forename: Mi-Kyung
authors.initials: MK
authors.lastname: Yun
authors.forename: Weixing
authors.initials: W
authors.lastname: Zhang
authors.forename: Vincent A
authors.initials: VA
authors.lastname: Boyd
authors.forename: Ariele
authors.initials: A
authors.lastname: Viacava Follis
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Griffith
authors.forename: Richard E
authors.initials: RE
authors.lastname: Lee
authors.forename: Donald
authors.initials: D
authors.lastname: Bashford
authors.forename: Stephen W
authors.initials: SW
authors.lastname: White
mesh_terms: D000494:Allosteric Regulation; D000495:Allosteric Site; D001408:Bacillus anthracis / Q000201:enzymology*; D001665:Binding Sites; D002384:Catalysis; D020134:Catalytic Domain; D019295:Computational Biology; D018360:Crystallography, X-Ray; D004094:Dihydropteroate Synthase / Q000737:chemistry* / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D011487:Protein Conformation; D020349:Surface Plasmon Resonance
chemical_list: D004791:Enzyme Inhibitors; D004094:Dihydropteroate Synthase