An arginine ladder in OprP mediates phosphate-specific transfer across the outer membrane.

Department of Biochemistry and Molecular Biology and the Center for Blood Research, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada.

The outer membrane protein OprP mediates the transport of essential phosphate anions into the pathogenic bacterium Pseudomonas aeruginosa. Here we report the crystallographic structure of trimeric OprP at 1.9-A resolution, revealing an unprecedented 9-residue arginine 'ladder' that spans from the extracellular surface down through a constriction zone where phosphate is coordinated. Lysine residues coat the inner periplasmic surface, creating an 'electropositive sink' that pulls the phosphates through the eyelet and into the cell.

PMID: 17187075 [PubMed - indexed for MEDLINE]