PDBsum entry: 1ek9

Membrane protein

PDB id: 1ek9

Contents

Protein chains

428 a.a. *

Waters ×1508

* Residue conservation analysis

PDB id:

1ek9

Name:

Membrane protein

Title:

2.1a x-ray structure of tolc: an integral outer membrane protein and efflux pump component from escherichia coli

Structure:

Outer membrane protein tolc. Chain: a, b, c. Engineered: yes

Source:

Escherichia coli. Organism_taxid: 562. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biol. unit:

Trimer (from PQS)

Resolution:

2.10Å R-factor: 0.208 R-free: 0.257

Authors:

V.Koronakis,A.J.Sharff,E.Koronakis,B.Luisi,C.Hughes

Key ref:

V.Koronakis et al. (2000). Crystal structure of the bacterial membrane protein TolC central to multidrug efflux and protein export. Nature, 405, 914-919. PubMed id: 10879525 DOI: 10.1038/35016007

Date:

07-Mar-00 Release date: 28-Jun-00

Protein chains

P02930  (TOLC_ECOLI) -  Outer membrane protein tolC

Seq: 493 a.a.

Struc: 428 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

 Gene Ontology (GO) functional annotation 

• Cellular component: membrane (5 terms)
• Biological process: transport (4 terms)
• Biochemical function: transporter activity (1 term)

DOI no: 10.1038/35016007

Nature 405:914-919 (2000)

PubMed id: 10879525

Crystal structure of the bacterial membrane protein TolC central to multidrug efflux and protein export.

V.Koronakis, A.Sharff, E.Koronakis, B.Luisi, C.Hughes.

ABSTRACT

Diverse molecules, from small antibacterial drugs to large protein toxins, are exported directly across both cell membranes of gram-negative bacteria. This export is brought about by the reversible interaction of substrate-specific inner-membrane proteins with an outer-membrane protein of the TolC family, thus bypassing the intervening periplasm. Here we report the 2.1-A crystal structure of TolC from Escherichia coli, revealing a distinctive and previously unknown fold. Three TolC protomers assemble to form a continuous, solvent-accessible conduit--a 'channel-tunnel' over 140 A long that spans both the outer membrane and periplasmic space. The periplasmic or proximal end of the tunnel is sealed by sets of coiled helices. We suggest these could be untwisted by an allosteric mechanism, mediated by protein-protein interactions, to open the tunnel. The structure provides an explanation of how the cell cytosol is connected to the external environment during export, and suggests a general mechanism for the action of bacterial efflux pumps.

Selected figure(s)

Figure 3.
Figure 3: Interfacial contacts in the alpha--helical barrel. a, View of selected contacts in the interface between H3/H4 and H7/H8. The contact made by Tyr 362 is well conserved in the TolC family. We propose that this contact is broken in the open state of the channel. b, Helical wheel representations summarizing the interhelical contacts in different parts of the -helical barrel. The register of lateral contacts between neighbouring helices at the top end of the helical barrel (left) can be maintained in a superhelix, whereas those at the proximal end, between sets of coiled coils (right), can only occur locally. Asterisks indicate the N-terminal residue of each helical segment.

Figure 5.
Figure 5: Exterior view of the proximal end of the alpha--helical barrel, approximately down the threefold symmetry axis. a, Crystal structure highlighting the coiled coils closing the proximal end of the tunnel. b, 'Open-state' model illustrating how the channel may be opened.

The above figures are reprinted by permission from Macmillan Publishers Ltd: Nature (2000, 405, 914-919) copyright 2000.

Figures were selected by an automated process.