Tetraloops are a type of four-base hairpin loop motifs in RNA secondary structure that cap many double helices. There are many variants of the tetraloop. The published ones include ANYA,
CUYG,
GNRA,
UNAC
and UNCG.
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, == UNCG ==
UNCG
In the UNCG is favorable thermodynamically and structurally due to hydrogen bonding, van der Waals interactions, coulombic interactions and the interactions between the RNA and the solvent. The UNCG tetraloops are more stable than DNA loops with the same sequence. The UUCG tetraloop is the most stable tetraloop. UUCG and GNRA tetraloops make up 70% of all tetraloops in 16S-rRNA . == CUUG ==
CUUG
The CUUG tetraloop has the highest likelihood of conformational changes due to its structural flexibility. Out of the three tetraloops mentioned, this tetraloop is the most flexible since the second uracil is comparatively unrestricted. It is also very thermodynamically stable. == See also ==