A number of genes that encode RNA-binding proteins belonging to the RNP family have been identified in cyanobacteria. All of them are predicted to encode small proteins with a single RNA recognition motif, containing both the RNP1 and RNP2 conserved motifs, and a short auxiliary motif which in many cases contains an abundance of glycine residues. Mutagenesis experiments to characterize the function of some of these gene products are being carried out. In Synechococcus sp. PCC 7942, interruption of the rbpA gene results in slower growth with an altered pigment composition.