IMES-2 RNA motif
The IMES-2 RNA motif is a conserved RNA structure that was identified by a study based on metagenomics and bioinformatics, and the underlying RNA sequences were identified independently by a similar earlier study. 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. IMES-2 RNAs are exceptionally abundant, as twice as many IMES-2 RNAs were found as ribosomes in RNAs sampled from the Pacific Ocean. Only two bacterial RNAs are known to be more highly transcribed than ribosomes.
The IMES-2 RNA secondary structure contains four stem-loop structures and one pseudoknot.