Proton and phosphorus NMR study of RNA self-complementary hexamers: influence of the 5-methylcytidine on the conformational transitions and the molecular motions.
We present proton and phosphorus NMR data, which contribute to explain why the 5-methylcytidine (m5C) differently affects the conformational transitions of CGUAm5CG (Bloch et al., FEBS Letters 219, 464 (1987)) and CGm5CGCG (Ceolin et al., J. Am. Chem. Soc. 109, 2539 (1987)). The atypical intermediate form observed in the random coil to A-like duplex transition of CGm5CGCG is determined: this original duplex structure exhibits a frame-shift pairing of the two strands, with a partial conservation of the A-type structure. In the case of CGUAm5CG such a pairing process would lead to a complete mismatch pairing. This feature probably explains that the NMR data of CGUACG and CGUAm5CG are similar and consistent with a random coil to A-type helix transition. Nevertheless a significant difference between the correlation times observed for the molecular motions of the two duplexes is detected. Another example of unusual conformational transition of methylated RNA oligomers is given by CAm5CGUG.
Bloch
G
G
Département de Biologie, Service de Biophysique, Gif-sur-Yvette Cedex, France.
Ceolin
F
F
Macquaire
F
F
Neumann
J M
JM
Babin
F
F
Huynh-Dinh
T
T
D001483:Base Sequence; D003562:Cytidine / Q000031:analogs & derivatives; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009690:Nucleic Acid Conformation; D010758:Phosphorus; D011522:Protons; D012313:RNA; D013816:Thermodynamics
D011522:Protons; D010758:Phosphorus; D003562:Cytidine; D012313:RNA; C016568:5-methylcytidine