[1] The RNAs are found only in bacteria classified as within the phylum Chlorobiota.

These RNAs are always in the 5' untranslated regions of operons that contain metK and ahcY genes.

metK genes encode methionine adenosyltransferase, which synthesizes S-adenosyl methionine (SAM), and ahcY genes encode S-adenosylhomocysteine hydrolase, which degrade the related metabolite S-Adenosyl-L-homocysteine (SAH).

The promoter sequences are commonly associated with strong transcription in the phyla Chlorobiota and Bacteroidota, but are not used by most lineages of bacteria.

The placement of SAM-Chlorobi RNAs suggests that they are involved in the regulation of the metK/ahcY operon through an unknown mechanism.