title: Global RNA Fold and Molecular Recognition for a pfl Riboswitch Bound to ZMP, a Master Regulator of One-Carbon Metabolism.
abstract: ZTP, the pyrophosphorylated analog of ZMP (5-amino-4-imidazole carboxamide ribose-5'-monophosphate), was identified as an alarmone that senses 10-formyl-tetrahydroflate deficiency in bacteria. Recently, a pfl riboswitch was identified that selectively binds ZMP and regulates genes associated with purine biosynthesis and one-carbon metabolism. We report on the structure of the ZMP-bound Thermosinus carboxydivorans pfl riboswitch sensing domain, thereby defining the pseudoknot-based tertiary RNA fold, the binding-pocket architecture, and principles underlying ligand recognition specificity. Molecular recognition involves shape complementarity, with the ZMP 5-amino and carboxamide groups paired with the Watson-Crick edge of an invariant uracil, and the imidazole ring sandwiched between guanines, while the sugar hydroxyls form intermolecular hydrogen bond contacts. The burial of the ZMP base and ribose moieties, together with unanticipated coordination of the carboxamide by Mg(2+), contrasts with exposure of the 5'-phosphate to solvent. Our studies highlight the principles underlying RNA-based recognition of ZMP, a master regulator of one-carbon metabolism.
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA.
authors.forename: Aiming
authors.initials: A
authors.lastname: Ren
authors.affiliation: Department of Chemistry and Chemical Biology, Cornell University, NE-CAT, Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA.
authors.forename: Kanagalaghatta R
authors.initials: KR
authors.lastname: Rajashankar
authors.affiliation: Structural Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10065, USA. Electronic address: pateld@mskcc.org.
authors.forename: Dinshaw J
authors.initials: DJ
authors.lastname: Patel
mesh_terms: D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000737:chemistry; D020029:Base Pairing; D002244:Carbon / Q000378:metabolism; D002413:Cations, Divalent; D000068536:Bacillota / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D008024:Ligands; D008274:Magnesium / Q000737:chemistry*; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D010710:Phosphates; D012265:Ribonucleotides / Q000737:chemistry*; D058928:Riboswitch / Q000235:genetics*; D013816:Thermodynamics; D014498:Uracil / Q000737:chemistry
chemical_list: D002413:Cations, Divalent; D008024:Ligands; D010710:Phosphates; D012265:Ribonucleotides; D058928:Riboswitch; D000620:Aminoimidazole Carboxamide; D014498:Uracil; D002244:Carbon; C098395:5-aminoimidazole-4-carboxamide-1-ribofuranosyl triphosphate; C031143:AICA ribonucleotide; D008274:Magnesium