RtmR is a membrane-embedded RRM-family RNA-binding protein

Here, using a genetic approach to identify negative regulators of biofilm formation in V. fischeri, we identified a membrane-bound RNA-binding protein, RtmR (VF_2432), that acts as an inhibitor of the symbiosis polysaccharide (SYP) biofilm. Membrane localization of the protein seems to be required for protein stability or expression, as truncation of the transmembrane helices led to an inability to detect the protein.

The conserved RNP1 and RNP2 motifs in RtmR’s cytoplasmic RNA recognition motif (RRM) domain are required for function, and we demonstrate binding to RNA substrates. Identification of RtmR RNA ligands was conducted with a iiCLIP-seq approach that revealed a large interactome. One transcript identified was that of the biofilm regulatory histidine kinase RscS.