Biophysical Society Thematic Meeting | Ascona, Switzerland

Liposomes, Exosomes, and Virosomes: From Modeling Complex Membrane Processes to Medical Diagnostics and Drug Delivery

Poster Abstracts

55-POS Board 28 The Outer Membrane Protein OprG of Pseudomonas aeruginosa Facilitates the Transport of Small Amino Acids Patrick Seelheim 1,2 , Iga Kucharska 1,2 , Lukas K. Tamm 1,2 . 2 University of Virginia, Charlottesville, VA, USA. 1 University of Virginia, Charlottesville, VA, USA, Pseudomonas aeruginosa is an opportunistic human pathogen that is responsible for a growing number of nosocomial infections and the main cause of death in patients with cystic fibrosis. Its very stable outer membrane lacks unspecific porins and poses an efficient permeation barrier to both hydrophilic and lipophilic compounds rendering P. aeruginosa resistant to many common antibiotics. The x-ray crystal structure of the P. aeruginosa outer membrane protein OprG revealed a tall 8- stranded β-barrel extending far into the extracellular space and featuring a proline-rich gate near the membrane interface. It has been speculated that this proline gate is involved in the transport of small hydrophobic compounds across the outer membrane. However, we found that OprG facilitates the transport of small, uncharged amino acids both in vitro and in vivo as shown by liposome swelling assays and P. aeruginosa growth curves. When determining the NMR solution structures of wild-type OprG and the transport incompetent P92A mutant OprG, we found shorter β-barrels with long disordered extracellular loops in both proteins. However, the P92A mutation led to an asymmetric elongation of the barrel and changes in the loop dynamics implying that unrestricted motion of loop 3 is required for amino acids transport.

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