The crystal structure of OprG from Pseudomonas aeruginosa, a potential channel for transport of hydrophobic molecules across the outer membrane.
BACKGROUND
The outer membrane (OM) of Gram-negative bacteria provides a barrier to the passage of hydrophobic and hydrophilic compounds into the cell. The OM has embedded proteins that serve important functions in signal transduction and in the transport of molecules into the periplasm. The OmpW family of OM proteins, of which P. aeruginosa OprG is a member, is widespread in Gram-negative bacteria. The biological functions of OprG and other OmpW family members are still unclear.


RESULTS
In order to obtain more information about possible functions of OmpW family members we have solved the X-ray crystal structure of P. aeruginosa OprG at 2.4 Å resolution. OprG forms an eight-stranded β-barrel with a hydrophobic channel that leads from the extracellular surface to a lateral opening in the barrel wall. The OprG barrel is closed off from the periplasm by interacting polar and charged residues on opposite sides of the barrel wall.


CONCLUSIONS
The crystal structure, together with recent biochemical data, suggests that OprG and other OmpW family members form channels that mediate the diffusion of small hydrophobic molecules across the OM by a lateral diffusion mechanism similar to that of E. coli FadL.
Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA.
Debra S
DS
Touw
Dimki R
DR
Patel
Bert
B
van den Berg
D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D018360:Crystallography, X-Ray; D057927:Hydrophobic and Hydrophilic Interactions; D007473:Ion Channels / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D008958:Models, Molecular; D019897:Periplasm / Q000378:metabolism; D011487:Protein Conformation; D017434:Protein Structure, Tertiary
D001425:Bacterial Outer Membrane Proteins; D007473:Ion Channels; C121501:OprG protein, Pseudomonas aeruginosa