Tetraloop
Tetraloops are a type of four-base
CUYG,[5] GNRA,[6] UNAC[7] and UNCG.[8]Three types of tetraloops are common in ribosomal RNA: GNRA, UNCG and CUUG, in which the N could be either uracil, adenine, cytosine, or guanine, and the R is either guanine or adenine. These three sequences form stable and conserved tetraloops that play an important role in structural stability and biological function of 16S rRNA.[9]
- GNRA
- The GNRA tetraloop has a guanine-adenine base-pair where the guanine is 5' to the helix and the adenine is 3' to the helix. Tetraloops with the sequence UMAC have essentially the same backbone fold as the GNRA tetraloop,[7] but may be less likely to form tetraloop-receptor interactions. They may therefore be a better choice for closing stems when designing artificial RNAs.
- The presence of the GNRA tetraloop provides an exceptional stability to RNA structure. GNRA occurs 50% more than other tetranucleotides due to their ability to withstand temperatures 4 °C higher than other RNA hairpins. This allows them to act as nucleation sites for proper folding of RNA. The rare hydrogen bonds between the first guanine and fourth adenine nucleotide, extensive stacking of nucleotide bases and hydrogen bonds between 2' OH of a ribose sugar and nitrogenous bases makes the tetraloop thermodynamically stable.[10]
- UNCG
- In the UNCG is favorable thermodynamically and structurally due to
- CUUG
See also
- Tetraloop-receptor interactions)
References
- S2CID 38185676.)
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