User:Michelle Meyer BC/L20

The structure of this family of ribosomal regulatory protein leaders was discovered independently both computationally and experimentally at the same time. Unlike its apparently non-homologous counterpart in Gammaproteobacteria, the Firmicute L20-interacting RNA regulates at the level of transcription, not translation The RNA structure is located in the 5' untranslated regions of mRNAs encoding initiation factor 3 followed by ribosomal proteins L35 and L20 (infC-rpmI-rplT). The Firmicute L20-interacting regulatory RNA consists of a 3-stem-loop structure, including a terminator stem. An additional non-binding stem was reported, but was only variably present and therefore not included in the consensus structure. Ribosomal protein L20 binds this leader sequence between the first two helices, and it is believed to function via a molecular mimicry model, due to its resemblance to the L20 binding site on the 23S rRNA.

The L20-binding RNA is most notably found in the Firmicute classes Bacilli and, to a lesser degree, Clostridia. Its presence in Thermotogae and Actinobacteria suggests possible horizontal transfer events.