PDBsum entry 2f1c

Membrane protein

PDB id: 2f1c

Contents

Protein chain

252 a.a.

Ligands

C8E ×2

Waters ×113

PDB id:

2f1c

Name:

Membrane protein

Title:

Crystal structure of the monomeric porin ompg

Structure:

Outer membrane protein g. Chain: x. Synonym: ompg. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 83333. Strain: k-12. Gene: ompg. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Dimer (from PQS)

Resolution:

2.30Å R-factor: 0.233 R-free: 0.260

Authors:

G.V.Subbarao,B.Van Den Berg

Key ref:

G.V.Subbarao and B.van den Berg (2006). Crystal structure of the monomeric porin OmpG. J Mol Biol, 360, 750-759. PubMed id: 16797588 DOI: 10.1016/j.jmb.2006.05.045

Date:

14-Nov-05 Release date: 27-Jun-06

Protein chain

P76045  (OMPG_ECOLI) -  Outer membrane porin G from Escherichia coli (strain K12)

Seq: 301 a.a.

Struc: 252 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.jmb.2006.05.045

J Mol Biol 360:750-759 (2006)

PubMed id: 16797588

Crystal structure of the monomeric porin OmpG.

G.V.Subbarao, B.van den Berg.

ABSTRACT

The outer membrane (OM) of Gram-negative bacteria contains a large number of channel proteins that mediate the uptake of ions and nutrients necessary for growth and functioning of the cell. An important group of OM channel proteins are the porins, which mediate the non-specific, diffusion-based passage of small (<600 Da) polar molecules. All porins of Gram-negative bacteria that have been crystallized to date form stable trimers, with each monomer composed of a 16-stranded beta-barrel with a relatively narrow central pore. In contrast, the OmpG porin is unique, as it appears to function as a monomer. We have determined the X-ray crystal structure of OmpG from Escherichia coli to a resolution of 2.3 A. The structure shows a 14-stranded beta-barrel with a relatively simple architecture. Due to the absence of loops that fold back into the channel, OmpG has a large ( approximately 13 A) central pore that is considerably wider than those of other E. coli porins, and very similar in size to that of the toxin alpha-hemolysin. The architecture of the channel, together with previous biochemical and other data, suggests that OmpG may form a non-specific channel for the transport of larger oligosaccharides. The structure of OmpG provides the starting point for engineering studies aiming to generate selective channels and for the development of biosensors.

Selected figure(s)

Figure 3.
Figure 3. Architecture of the OmpG pore. (a) Stereo backbone representation of OmpG in a direction perpendicular to the membrane and viewed from the extracellular side, showing the charged and aromatic residues in the pore constriction, with 2F[o] – F[c] electron density for the side-chains in blue, contoured at 1.2 σ. Residue numbers are indicated. (b) Surface representations of the OmpG channel viewed from the extracellular side (left, orientation similar to that in (a)) and the periplasmic side (right), showing the electrostatic surface potentials inside the channel. The surface is colored blue for potentials > 15 kT/e and red for potentials < –15 kT/e. The Figure was generated with GRASP.^38

Figure 5.
Figure 5. Stereo backbone representation of E. coli OmpG from the extracellular side, showing the distribution of aromatic (grey) and charged residues (red, glutamic acid 15/17/31/52/152/174; blue, arginine 68/92/111/150) on the extracellular side of the constriction. The numbers of the aromatic residues (Y50, F66, Y94, Y96, Y98, F132, Y136 and Y146) that may provide binding sites for oligosaccharides are indicated. For clarity, the barrel has been tilted and only residues present on one side of the constriction are shown.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2006, 360, 750-759) copyright 2006.

Figures were selected by an automated process.