title: Eu(III) macrocyclic complexes promote cleavage of and bind to models for the 5'-cap of mRNA. Effect of pendent group and a second metal ion.
abstract: The interaction of three Eu(III) macrocyclic complexes Eu(THED)3+, Eu(ATHC)3+, and Eu(ATHC)3+, and Eu(S-THP)3+ with two 5'-cap model compounds, GpppG and m7GpppG is studied (THED = 1,4,7,10-tetrakis(2-hydroxyethyl)-1,4,7,-10-tetraazacyclododecane, ATHC = 1-(carbamoylmethyl)-4,7,10-tris(2-hydroxyethyl)-1,4,7,10- tetraazacyclododecane, S-THP = 1S,4S,7S,10S-tetrakis(2-hydroxypropyl)-1,4,7,10-tetraazacyclododecane). Laser-induced excitation luminescence spectroscopy is used to study the binding of Eu(S-THP)3+ to GpppG (K = 5.9 x 10(4) M-1) and to characterize the Eu(S-THP)-GpppG complex. Both Eu(THED)3+ and Eu(S-THP)3+ bind to m7GpppG as monitored by use of fluorescence spectroscopy with binding constants of 5.9 x 10(3) and 4.4 x 10(4) M-1, respectively. The kinetics of cleavage of GpppG by two macrocyclic complexes is studied. Cleavage of GpppG by Eu(THED)3+ is accelerated by 15-fold in the presence of an equivalent of Zn(NO3)2 at pH 7.3, 37 degrees C, suggesting that two metal ions accelerate the cap cleavage reaction. Eu(ATHC)3+ promotes cleavage of GpppG with a pseudo-first-order rate constant of 2.6 x 10(-5) s-1 at pH 7.3, 37 degrees C, and 0.30 mM complex.
authors.affiliation: Department of Chemistry, State University of New York at Buffalo, Amherst, New York 14260, USA.
authors.forename: D M
authors.initials: DM
authors.lastname: Epstein
authors.forename: L L
authors.initials: LL
authors.lastname: Chappell
authors.forename: H
authors.initials: H
authors.lastname: Khalili
authors.forename: R M
authors.initials: RM
authors.lastname: Supkowski
authors.forename: W D
authors.initials: WD
authors.lastname: Horrocks
authors.forename: J R
authors.initials: JR
authors.lastname: Morrow
mesh_terms: D000465:Algorithms; D005063:Europium / Q000737:chemistry*; D006150:Guanine Nucleotides / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012315:RNA Caps / Q000737:chemistry; D012333:RNA, Messenger / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry
chemical_list: D006150:Guanine Nucleotides; D009942:Organometallic Compounds; D012315:RNA Caps; D012333:RNA, Messenger; D005063:Europium; D015032:Zinc