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Development of Novel Small Molecule Antibiotics against a Conserved RNA Element in Gram‐positive Bacteria
Author(s) -
Väre Ville Y.P.,
Frohlich Kyla M.,
Todd Gabrielle,
Bell Janeen,
Agris Paul F.
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.608.12
Subject(s) - riboswitch , biology , aminoacylation , transfer rna , antitermination , rna , biochemistry , transcription (linguistics) , bacterial transcription , gene , rna polymerase , non coding rna , linguistics , philosophy
tRNA‐dependent control of gene expression, T‐boxes, are RNA regulatory elements located at the 5′‐untranslated region (5′‐UTR) in numerous gram‐positive bacteria. T‐boxes control the expression of several genes involved in tRNA aminoacylation, as well as amino acid metabolism and transport. T‐boxes function by recognizing the aminoacylation status of their cognate tRNA ligand: uncharged tRNA can stabilize an antiterminator complex through an acceptor stem – antiterminator interaction, thus allowing transcription of the downstream operon. Aminoacylated tRNA cannot form this interaction, therefore the thermodynamically more stable terminator hairpin is formed, causing transcription to halt. Given that T‐boxes are found exclusively in gram‐positive bacteria and share highly conserved regions necessary for tRNA binding, this RNA regulatory element represents a prime target for antibacterial drug development. Docking studies using atomic‐resolution T‐box structures identified several potential candidates. 43 putative antibacterial compounds representing distinct chemical families were selected for further characterization. Antibacterial microdilution studies resulted in a moderately active hit compound (PKZ18) that has been selected for further antibacterial drug development. Characterization studies demonstrate that PKZ18 is highly refractory to resistance, displays low cytotoxicity, and possesses activity against a wide range of gram‐positive bacteria, including clinical isolates of Staphylococcus aureus , Streptococcus pyogenes , and Clostridium difficile . Mechanism of action studies confirm binding of PKZ18 to both glycine and tyrosine T‐boxes, as well as inhibition of threonine tRNA synthetase, a protein under the control of a threonine T‐box in S. aureus . Structure‐activity relationship (SAR) studies of PKZ18 have identified the essential chemical moieties for both specificity as well as activity. Hit‐to‐lead optimization of PKZ18 by medicinal chemistry and further SAR studies is on‐going.