The ribosomal protein family L20 contains members from eubacteria, as well as their mitochondrial and plastid homologs. L20 is an assembly protein, required for the first in-vitro reconstitution step of the 50S ribosomal subunit, but does not seem to be essential for ribosome activity. L20 has been shown to partially unfold in the absence of RNA, in regions corresponding to the RNA-binding sites. L20 represses the translation of its own mRNA via specific binding to two distinct mRNA sites, in a manner similar to the L20 interaction with 23S ribosomal RNA.
Jiyao W et al.(2023). "The conserved domain database in 2023.",