Function
A translational regulator that binds mRNA to regulate translation initiation and/or mRNA stability. Post-transcriptionally represses the expression of genes controlled by GacA/GacS (PubMed:10570200, PubMed:15601712, PubMed:11807065, PubMed:23635605). Represses expression of hcnA; alterations in the ribosome-binding site relieve the repression (PubMed:10570200). Binds specifically to small RNAs (sRNA) RsmX, RsmZ and RsmY; these sRNAs fold into secondary structures with multiple GGA sequence in loops to which the CsrA proteins bind (PubMed:11807065, PubMed:14622422, PubMed:16286659). Binding to RsmX, RsmY or RsmZ titrates the protein so that it can no longer bind mRNA and repress translation; each sRNA can bind more than one protein (PubMed:14622422, PubMed:16286659). Required for optimal expression and stability of sRNAs RsmX, RsmY and RsmZ (PubMed:15601712, PubMed:16286659). Deletion of rsmY or rsmZ alone has no detectable phenotype, but a double sRNA deletion has a marked decrease in production of secondary metabolites HCN, exoprotease AprA, antifungal agent 2,4-diacetylphloroglucinol and protects cucumber plants from fungal infection less well than wild-type (PubMed:14622422). The triple sRNA deletion has even stronger loss of these phenotypes (PubMed:16286659).