Spatial configuration of the bizarre 5' terminus of mammalian mRNA

Preparation and Properties of mRNA 5-cap Structure

“…Table 2 summarizes conformational parameters of 7-methylguanosine nucleotides in solution. Unlike other purine nucleosides and nucleotides, 7-methylguanosine and its 5´-phosphorylated derivatives prefer a 3´-endo sugar ring conformation [26][27][28][29][30][31]. With 7-methylguanosine, the proportion of the 3´-endo conformers is 50 %, whereas guanosine preferably exists in a 2´-endo conformation (38 % 3´-endo).…”

“…With 7-methylguanosine, the proportion of the 3´-endo conformers is 50 %, whereas guanosine preferably exists in a 2´-endo conformation (38 % 3´-endo). The proportion of 3´-endo conformers increases upon 5´-phosphorylation and is dependent on the number of phosphate groups [26,27]. As guanosine, guanosine 5´-phosphates prefer 2´-endo conformation under neutral conditions [26].…”

High resolution nuclear magnetic resonance studies of platinum(II) – guanosine-5′-monophosphate interactions in aqueous solutions

“…The high field spectra were analyzed by the first order method, which for G5'p gave parameters, are identical to those obtained from computer fits of spectra recorded at lower field (10,11). In the case of [PtC1,(G5'p)]-and [PtCl2(G5'p),], however, the signal of H(3') appears as a triplet instead of a quartet.…”

“…The downfield shift of H (8) for [PtC1,(G5'p)]-appears to be a direct consequence of platinum binding at N7 which produces a polarizing effect of the C-H (8) bond towards the imidazole ring causing it to become electron deficient (11,12), hence the use of the abbreviation Pt7GS'p. The downfield shift of 0.202ppm observed for Pt7G5'p is somewhat less than the value of 0.858ppm determined for protonation of G5'p at N7 (Table 1) but is nevertheless compatible with a certain degree of positive character on the imidazole ring.…”

“…Thus N7 platination and methylation (or protonation) of GS'p produce opposite conformational changes. The conformational change determined for m7G5 'p was explained in terms of an electrostatic attraction involving the positively charge imidazole ring and the phosphate group (11). The opposite conformational change determined for pt7Gs'p (from gg 4 gt (or tg)) can adequately be rationalized in terms of an electrostatic repulsion between the phosphate group and the platinum halide moiety.…”