This family represents a conserved region approximately 400 residues long within the bacterial phosphate-selective porins O and P. These are anion-specific porins, the binding site of which has a higher affinity for phosphate than chloride ions. Porin O has a higher affinity for polyphosphates, while porin P has a higher affinity for orthophosphate. In P. aeruginosa, porin O was found to be expressed only under phosphate-starvation conditions during the stationary growth phase.
Jiyao W et al.(2023). "The conserved domain database in 2023.",