title: Rapid kinetics of iron responsive element (IRE) RNA/iron regulatory protein 1 and IRE-RNA/eIF4F complexes respond differently to metal ions.
abstract: Metal ion binding was previously shown to destabilize IRE-RNA/IRP1 equilibria and enhanced IRE-RNA/eIF4F equilibria. In order to understand the relative importance of kinetics and stability, we now report rapid rates of protein/RNA complex assembly and dissociation for two IRE-RNAs with IRP1, and quantitatively different metal ion response kinetics that coincide with the different iron responses in vivo. kon, for FRT IRE-RNA binding to IRP1 was eight times faster than ACO2 IRE-RNA. Mn(2+) decreased kon and increased koff for IRP1 binding to both FRT and ACO2 IRE-RNA, with a larger effect for FRT IRE-RNA. In order to further understand IRE-mRNA regulation in terms of kinetics and stability, eIF4F kinetics with FRT IRE-RNA were determined. kon for eIF4F binding to FRT IRE-RNA in the absence of metal ions was 5-times slower than the IRP1 binding to FRT IRE-RNA. Mn(2+) increased the association rate for eIF4F binding to FRT IRE-RNA, so that at 50 µM Mn(2+) eIF4F bound more than 3-times faster than IRP1. IRP1/IRE-RNA complex has a much shorter life-time than the eIF4F/IRE-RNA complex, which suggests that both rate of assembly and stability of the complexes are important, and that allows this regulatory system to respond rapidly to change in cellular iron.
authors.affiliation: Department of Chemistry and Biochemistry, Hunter College, City University of New York, New York, NY 10065, USA.
authors.forename: Mateen A
authors.initials: MA
authors.lastname: Khan
authors.affiliation: Department of Chemistry and Biochemistry, Hunter College, City University of New York, New York, NY 10065, USA.
authors.forename: Jia
authors.initials: J
authors.lastname: Ma
authors.affiliation: Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL 60612-7334, USA.
authors.forename: William E
authors.initials: WE
authors.lastname: Walden
authors.affiliation: Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Merrick
authors.affiliation: Childeren's Hospital Oakland Research Institute, Oakland, CA 94609, USA.
authors.forename: Elizabeth C
authors.initials: EC
authors.lastname: Theil
authors.affiliation: Department of Chemistry and Biochemistry, Hunter College, City University of New York, New York, NY 10065, USA dgoss@hunter.cuny.edu.
authors.forename: Dixie J
authors.initials: DJ
authors.lastname: Goss
mesh_terms: D000154:Aconitate Hydratase / Q000235:genetics / Q000378:metabolism; D000818:Animals; D039562:Eukaryotic Initiation Factor-4F / Q000378:metabolism*; D005293:Ferritins / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D035941:Iron Regulatory Protein 1 / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D008345:Manganese / Q000737:chemistry; D011188:Potassium / Q000737:chemistry; D012333:RNA, Messenger / Q000737:chemistry* / Q000378:metabolism*; D011817:Rabbits; D038621:Regulatory Sequences, Ribonucleic Acid
chemical_list: D039562:Eukaryotic Initiation Factor-4F; D012333:RNA, Messenger; D038621:Regulatory Sequences, Ribonucleic Acid; D008345:Manganese; D005293:Ferritins; D007501:Iron; D000154:Aconitate Hydratase; D035941:Iron Regulatory Protein 1; D011188:Potassium
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