The IMES-2 RNA motif is a conserved RNA structure that was identified by a study based on metagenomics and bioinformatics,[1] and the underlying RNA sequences were identified independently by a similar earlier study.[2] These RNAs are present in environmental sequences, and when discovered were not known to be present in any cultivated species. However, an IMES-2 RNA has been detected in alphaproteobacterium HIMB114, which is classified in the SAR11 clade of marine bacteria. This finding fits with earlier predictions that species that use IMES-2 RNAs are most closely related to alphaproteobacteria.[2] IMES-2 RNAs are exceptionally abundant, as twice as many IMES-2 RNAs were found as ribosomes[1] in RNAs sampled from the Pacific Ocean.[2] [3] Only two bacterial RNAs are known (6S RNA and transfer RNA) to be more highly transcribed than ribosomes.
The IMES-2 RNA secondary structure contains four stem-loop structures and one pseudoknot.