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Structure of a GNRA tetraloop from a group I self-splicing intron.[1]

Tetraloops are a type of four-base hairpin loop motifs in RNA secondary structure that cap many double helices.[2] Three types of tetraloops are common in ribosomal RNA: GNRA, UNCG and CUUG. 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, [3] but may be less likely to form tetraloop-receptor interactions. They may therefore be a better choice for closing stems when designing artificial RNAs.

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  1. ^ Cate, J.H., Gooding, A.R., Podell, E., Zhou, K., Golden, B.L., Kundrot, C.E., Cech, T.R., Doudna, J.A. (1996). "Crystal structure of a group I ribozyme domain: principles of RNA packing.". Science 273 (5282): 1676–1685. doi:10.1126/science.273.5282.1678. PMID 8781224. 
  2. ^ Woese, C.R., Winkers, S., Gutell, R.R. (1990). "Architecture of ribosomal RNA: Constraints on the sequence of "tetra-loops"". Proc. Nati. Acad. Sci. USA 87 (21): 8467–71. doi:10.1073/pnas.87.21.8467. PMC 54977. PMID 2236056. 
  3. ^ Zhao, Q., Huang, H-C., Nagaswamy, U., Xia, Y., Gao, X., Fox, G.E. (2012). "UNAC tetraloops: To what extent do they mimic GNRA tetraloops?". Biopolymers 97 (8): 617–628. doi:10.1002/bip.22049. PMID 22605553.