The
5S ribosomal RNA (
5S rRNA) is an approximately 120 nucleotide-long
ribosomal RNA molecule with a mass of 40
kDa. It is a structural and functional component of the large subunit of the
ribosome in all domains of life (
bacteria,
archaea, and
eukaryotes), with the exception of mitochondrial ribosomes of
fungi and
animals. The designation 5S refers to the molecule’s
sedimentation velocity in an ultracentrifuge, which is measured in
Svedberg units (S).