Tetraloop

A tetraloop, in the context of RNA secondary structure, refers to a four-nucleotide (tetramer) loop structure found at the end of hairpin loops. These short loops are common and can contribute significantly to the stability of RNA molecules. Certain tetraloop sequences are known to be particularly stable and are frequently found across different RNA molecules. These stable tetraloops often possess specific structural motifs. The stability is derived from base-stacking interactions within the loop itself and often involves hydrogen bonding beyond standard Watson-Crick pairing. The sequence and specific conformation of a tetraloop can influence its interactions with proteins and other RNA molecules, thereby playing a crucial role in various biological processes. Common and stable tetraloops include, but are not limited to, UNCG, where N represents any nucleotide. The specific identity of N can modulate the loop's properties. The relative stability and prevalence of different tetraloop sequences have been extensively studied using experimental and computational methods.