Investigating the Structure-Function Relationship of the Phosphate-Selective Channel OprP

Abstract

The outer membrane porin OprP of Pseudomonas aeruginosa is a highly phosphate-selective channel. It is induced under the condition of phosphate starvation and facilitates the high-affinity uptake of phosphate ions across the outer membrane of bacteria [1]. An investigation of the structure-function relationship of OprP is required to understand the anion and phosphate selectivity of this porin in particular and to expand the present understanding of ion selectivity of different channels in general. To this end, we investigated the wild-type OprP and several important mutants of OprP to decode the phosphate selectivity of the channel [2, 3]. Mutants helped to probe the individual contribution of important residues toward the selectivity of OprP. Both electrophysiological bilayer measurements and free-energy molecular dynamics (MD) simulations were carried out to monitor the change in ion selectivity and phosphate binding affinity of various mutants compared to wild-type OprP. Results obtained from MD simulations were in qualitative agreement with experiments and complemented experimental observations by providing atomistic details regarding function and dynamics of OprP. Molecular details learned from such studies could be exploited to engineer the channel for various applications [4, 5].[1] R. E. W. Hancock, K. Poole, R. Benz, J. Bacteriol. 150, 730-738 (1982).[2] N. Modi, R. Benz, R. E. W. Hancock, U. Kleinekathofer, J. Phys. Chem. Lett. 3, 3639-3645 (2012).[3] N. Modi, I. Barcena-Uribarri, M. Bains, R. Benz, R. E. W. Hancock, U. Kleinekathofer, Biochemistry. 52, 5522-5532 (2013).[4] P. Pongprayoon, O. Beckstein, M. S. P. Sansom, J. Phys. Chem. B. 116, 462-268 (2011).[5] N. Modi, M. Winterhalter, and U. Kleinekathofer, Nanoscale 4, 6166-6180 (2012).