Structural domains comprising this sueprfamily share the structure of the highly conserved bacterial translational regulator protein CsrA. This RNA-binding protein acts by regulating translation and stability of mRNAs which code for proteins involved in metabolism and virulence PMID:23954502. CsrA is a dimer of two identical subunits, each composed of five strands, a small alpha-helix and a flexible C terminus.

CsrA destabilizes target mRNAs by binding in a region within the -18 and +31 nucleotides of the coding region, which includes the ribosome-binding site. This prevents translation of the corresponding mRNA and promotes its degradation by endogenous RNases. The intracellular levels of CsrA are regulated by two untranslated RNA molecules, CsrB and CsrC, that act as antagonists by sequestering CsrA and preventing its binding to target mRNAs PMID:15866937. .