title: X-ray crystal structures of the Escherichia coli RNA polymerase in complex with benzoxazinorifamycins.
abstract: Rifampin, a semisynthetic rifamycin, is the cornerstone of current tuberculosis treatment. Among many semisynthetic rifamycins, benzoxazinorifamycins have great potential for TB treatment due to their superior affinity for wild-type and rifampin-resistant Mycobacterium tuberculosis RNA polymerases and their reduced hepatic Cyp450 induction activity. In this study, we have determined the crystal structures of the Escherichia coli RNA polymerase complexes with two benzoxazinorifamycins. The ansa-naphthalene moieties of the benzoxazinorifamycins bind in a deep pocket of the β subunit, blocking the path of the RNA transcript. The C3'-tail of benzoxazinorifamycin fits a cavity between the β subunit and σ factor. We propose that in addition to blocking RNA exit, the benzoxazinorifamycin C3'-tail changes the σ region 3.2 loop position, which influences the template DNA at the active site, thereby reducing the efficiency of transcription initiation. This study supports expansion of structure-activity relationships of benzoxazinorifamycins inhibition of RNA polymerase toward uncovering superior analogues with development potential.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Center for RNA Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Vadim
authors.initials: V
authors.lastname: Molodtsov
authors.forename: Irosha N
authors.initials: IN
authors.lastname: Nawarathne
authors.forename: Nathan T
authors.initials: NT
authors.lastname: Scharf
authors.forename: Paul D
authors.initials: PD
authors.lastname: Kirchhoff
authors.forename: H D Hollis
authors.initials: HD
authors.lastname: Showalter
authors.forename: George A
authors.initials: GA
authors.lastname: Garcia
authors.forename: Katsuhiko S
authors.initials: KS
authors.lastname: Murakami
mesh_terms: D000904:Antibiotics, Antitubercular; D018360:Crystallography, X-Ray; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000235:genetics; D024881:Drug Resistance, Bacterial; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D020035:Holoenzymes / Q000737:chemistry; D008958:Models, Molecular; D009154:Mutation; D011487:Protein Conformation; D012294:Rifamycins / Q000138:chemical synthesis / Q000737:chemistry*; D014158:Transcription, Genetic
chemical_list: D000904:Antibiotics, Antitubercular; D029968:Escherichia coli Proteins; D020035:Holoenzymes; D012294:Rifamycins; C068980:KRM 1648; D012321:DNA-Directed RNA Polymerases