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Liposomes, Exosomes, and Virosomes: From Modeling Complex
Membrane Processes to Medical Diagnostics and Drug Delivery
Poster Abstracts
70
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.