A Comparison on the Coordination Tendency towards Cu²⁺ of the Base Moieties in Guanosine, Inosine and Adenosine 5′‐Triphosphates

Abstract

The chemical shift of the proton H(8) in the proton magnetic resonance spectrum of GTP was measured in aqueous solution in dependence on pH (2 to 12). Based hereon the acidity constants for protonation at N(7) and deprotonation at N( 1) were determined. From the line broadening effects in the presence of Cu2+ it is concluded that this metal ion interacts with N(7) of the guanine moiety in Cu(GTP)2-. Hence, the structure of this latter complex corresponds to the one of Cu(ATP)2-, while in Cu(1TP)Z-only a very minor interaction with N(7) occurs (cf. Eur. J. Biochem. 41, [I9741 209-216). There is also evidence that in the complex CU(GTP-~H)~-a 5-membered chelate involving N(7) and O(6) is formed, while in Cu(ITP-IH)3-the interaction with Cu2+ occurs only with the N(1), O(6)-site of the base moiety. The decrease in line broadening observed at higher pH indicates that the Cuz+-nucleic-base interaction is depressed in CU(ATP)(OH)~-, Cu(GTP-1 H)(OH)4-and Cu(1TP-1H)(OH)4-, as well. In all the mixed-ligand systems which consist of Cu2+, 2,2'-bipyridyl (Bipy) and one of the three nucleotides (NTP) the ternary complexes, Cu(Bipy) (NTP)2-, are formed. Within these ternary complexes a charge-transfer interaction occurs between the purine part of the nucleotides and 2,2'-bipyridyl.Recent studies on the dephosphorylation of the binary and ternary complexes, Cu(ATP)2-and Cu-(Bipy)(ATP)2-[1,2], and the extension of this work to the corresponding complexes with ITP4-and GTP4-

Ternary complexes in solution. XXIV. Metal ion bridging of stacked purine-indole adducts. The mixed-ligand complexes of adenosine 5'-triphosphate, tryptophan, and manganese(II), copper(II), or zinc(II)

“…The metal ion used was Cu2+, and the ligands were 2,2'-bipyridyl and the S'-triphosphates of adenosine,24-25 inosine,24•25 or guanosine. 26 In the resulting ternary complexes, Cu2+ is coordinated to the nitrogen donors of 2,2'-bipyridyl and to the phosphate chain of the nucleotides, and the dominant configuration is that which allows stacking between the aromatic amine and the purine moiety.…”