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Structures of sequential open states in a symmetrical opening transition of the TolC exit duct

DOI: 10.1073/pnas.1012588108 DOI Help
PMID: 21245342 PMID Help

Authors: Xue-yuan Pei (University of Cambridge) , Philip Hinchliffe (University of Cambridge) , Martyn F. Symmons (University of Cambridge) , Eva Koronakis (University of Cambridge) , Roland Benz (University of Cambridge) , Colin Hughes (University of Cambridge) , Vassilis Koronakis (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Proceedings Of The National Academy Of Sciences , VOL 108 (5) , PAGES 2112 - 2117

State: Published (Approved)
Published: February 2011

Abstract: In bacterial drug resistance and virulence pumps, an inner membrane (IM) transporter and periplasmic adaptor recruit an outer membrane (OM) trimeric TolC exit duct that projects an ?-helical tunnel across the periplasm. The TolC periplasmic entrance is closed by densely packed ?-helical coiled coils, inner H7/H8, and outer H3/H4, constrained by a hydrogen bond network. On recruitment, these coiled coils must undergo transition to the open state. We present 2.9 Å resolution crystal structures of two sequential TolC open states in which the network is incrementally disrupted and channel conductances defined in lipid bilayers. Superimposition of TolCRS (370 pS) and TolCYFRS (1,000 pS) on the TolCWT closed state (80 pS) showed that in the initial open-state TolCRS, relaxation already causes approximately 14° twisting and expansion of helix H7 at the periplasmic tip, increasing interprotomer distances from 12.2 Å in TolCWT to 18.9 Å. However, in the crystal structure, the weakened Asp374 pore constriction was maintained at the closed state 11.3 Å2. In the advanced open-state TolCYFRS, there was little further expansion at the tip, to interprotomer 21.3 Å, but substantial movement of inner and outer coiled coils dilated the pore constriction. In particular, upon abolition of the TolCYFRS intraprotomer Tyr362–Asp153 link, a redirection of Tyr362 and “bulge” in H3 allowed a simple movement outward of H8, establishing a 50.3 Å2 opening. Root mean square deviations (rmsds) over the coiled coils of the three protomers of TolCRS and TolCYFRS illustrate that, whereas independent movement at the periplasmic tips may feature in the initial stages of opening, full dilation of the pore constriction is entirely symmetrical.

Journal Keywords: Biological; Escherichia; Lipid; Membrane Transport Proteins

Subject Areas: Biology and Bio-materials


Instruments: I02-Macromolecular Crystallography

Added On: 08/06/2015 09:53

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