N2-Methylguanine is a modified nucleoside. N2-Methylguanine is an endogenous methylated nucleoside found in human fluids.
N2-methylguanine is found within both helical and looped regions of RNA secondary structure, and it can exist in either the s-cis or the s-trans rotamer. If there is a rotational preference for the methyl group, the effect of N2-methylguanine substitution may be specific to the sequence context depending upon which face of the base participates in hydrogen bonding[1]. N2-methylguanine is the principal kinetic barrier for reverse transcription in the 1340 bases proximal to the 5' end of E. coli 16S rRNA. Transcription intermediates correspond to attenuation at the positions of N2-methylguanine in the rRNA sequence. The relaxation time for elongation of the cDNA through m2G is approximately 3 min[2].
[1]. Rife JP, et al. N 2-methylguanosine is iso-energetic with guanosine in RNA duplexes and GNRA tetraloops. Nucleic Acids Res. 1998 Aug 15;26(16):3640-4. [2]. Youvan DC, et al. Reverse transcriptase pauses at N2-methylguanine during in vitro transcription of Escherichia coli 16S ribosomal RNA. Proc Natl Acad Sci U S A. 1979 Aug;76(8):3751-4.