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Channel-tunnels
V Koronakis1, C Andersen, C Hughes
1Department of Pathology, Cambridge University, Tennis Court Road, Cambridge CB2 1QP, UK. vk103@mole.bio.cam.ac.uk
Current Opinion in Structural Biology
|August 10, 2001
Summary
TolC proteins form a channel in bacterial outer membranes for substrate export. This channel opens via an iris-like mechanism when interacting with specific proteins.
Area of Science:
- Microbiology
- Structural Biology
- Biochemistry
Background:
- TolC and its homologues are essential outer membrane proteins in bacteria.
- These proteins form a transperiplasmic tunnel facilitating the efflux of various substrates.
- The structure involves an alpha-helical tunnel connected to a beta-barrel channel.
Purpose of the Study:
- To elucidate the structural and functional mechanism of the TolC channel.
- To understand how the periplasmic entrance of the channel is regulated.
- To investigate the role of substrate-engaged proteins in channel opening.
Main Methods:
- Structural analysis of TolC and related proteins.
- Biochemical assays to study substrate binding and transport.
- In vitro reconstitution of the channel and its regulatory components.
Main Results:
- TolC forms a contiguous channel through the bacterial outer membrane.
- The periplasmic entrance of the channel is typically closed.
- An 'iris-like' mechanism opens the channel upon recruitment by cytosolic proteins.
Conclusions:
- TolC functions as a major bacterial efflux pump.
- Channel gating is regulated by an iris-like mechanism at the periplasmic entrance.
- This mechanism allows for controlled substrate export in response to cellular signals.