Remodeling of the DNA backbone promotes nucleotide flipping of the lesion and the complementary base into the solvent and toward the protein surface, respectively.
More significantly, a new interaction occurs between the backbone of nucleotide 5 and R41, at the extreme N-terminus of the helix-loop-helix motif in chain H.
This suggestion is then bolstered by the observations of DNA binding at the geminate interface, with a specific interaction between R41, at the extreme N-terminal end of the helix-turn-helix motif, and the DNA backbone of nucleotide 5.
Arg237 and Arg238 in E. coli GlnRS, which interact with the sugar phosphate backbone at nucleotide G5, are replaced by Asp237 and Glu238 in GluRS.
Compared with the structure of the DENV4 helicase complexed with a 12-mer RNA (Luo et al., 2008), the sugar-phosphate backbone of nucleotides 1 3 is more extended in the ZIKV helicase.
The PPP is the major source of ribose-5-phosphate, which constitutes the sugar backbone of nucleotides.
The contiguous pair of invariant arginine residues 1075 and 1076 straddles the ribose-phosphate backbone between nucleotides three and four from the 3′-end of the RNA primer.
The main source of NADPH is the PPP, which converts glucose-6-phosphate to ribose-5-phosphate, the sugar backbone of nucleotides.
This explains the high growth rate in PPG and TIG at 48 h, since cells in these groups produced more d-ribose-5-phosphate (R5P, the sugar backbone of nucleotides) to support rapid growth [ 25, 26] (The PLS analysis for cell growth is given in Additional file 6: Figure S3).
We therefore postulated that by manipulating the nucleotide backbone and fine tuning the duplex stability through modified nucleotide chemistry, it may be possible to significantly modulate many characteristics of the system, such as binding affinity, specificity, stability, in vitro and cellular activity, which would be crucial for development of efficacious CRISPR-based therapeutic entities.
