Modeling the Ion Selectivity of the Phosphate Specific Channel OprP

Ion selectivity of transport systems is an essential property of membranes from living organisms. These entities are used to regulate multifarious biological processes by virtue of selective participation of specific ions in transport processes. To understand this process, we studied the phosphate selectivity of the OprP porin from Pseudomonas aeruginosa using all-atom free-energy molecular dynamics simulations. These calculations were performed to define the energetics of phosphate, sulfate, chloride, and potassium ion transport through OprP. Atomic-level analysis revealed that the overall electrostatic environment of the channel was responsible for the anion selectivity of the channel, whereas the particular balance of interactions between the permeating ions and water as well as channel residues drove the selectivity between different anions. The selectivity of OprP is discussed in light of well-studied ion channels that are highly selective for potassium or chloride.