2XMN

High resolution snapshots of defined TolC open states present an iris- like movement of periplasmic entrance helices

Summary for 2XMN

• Entry DOI: 10.2210/pdb2xmn/pdb
• Related: 1EK9 1TQQ 2VDD 2VDE 2WMZ
• Descriptor: Outer membrane protein TolC, CHLORIDE ION, DODECYL-BETA-D-MALTOSIDE, ... (4 entities in total)
• Functional Keywords: transport protein, outer-membrane, drug-efflux, type-i secretion
• Biological source: Escherichia coli (strain K12)
• Total number of polymer chains: 3
• Total formula weight: 141370.14

Authors

Pei, X.Y.,Koronakis, E.,Hughes, C.,Koronakis, V. (deposition date: 2010-07-28, release date: 2011-01-26, Last modification date: 2023-12-20)

Primary citation

Pei, X.Y.,Hinchliffe, P.,Symmons, M.F.,Koronakis, E.,Benz, R.,Hughes, C.,Koronakis, V.
Structures of sequential open states in a symmetrical opening transition of the TolC exit duct.
Proc. Natl. Acad. Sci. U.S.A., 108:2112-2117, 2011

PubMed 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 α-helical tunnel across the periplasm. The TolC periplasmic entrance is closed by densely packed α-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 TolC(RS) (370 pS) and TolC(YFRS) (1,000 pS) on the TolC(WT) closed state (80 pS) showed that in the initial open-state TolC(RS), relaxation already causes approximately 14° twisting and expansion of helix H7 at the periplasmic tip, increasing interprotomer distances from 12.2 Å in TolC(WT) to 18.9 Å. However, in the crystal structure, the weakened Asp(374) pore constriction was maintained at the closed state 11.3 Å(2). In the advanced open-state TolC(YFRS), 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 TolC(YFRS) intraprotomer Tyr(362)-Asp(153) link, a redirection of Tyr(362) and "bulge" in H3 allowed a simple movement outward of H8, establishing a 50.3 Å(2) opening. Root mean square deviations (rmsds) over the coiled coils of the three protomers of TolC(RS) and TolC(YFRS) 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.

PubMed: 21245342
DOI: 10.1073/pnas.1012588108

Experimental method

X-RAY DIFFRACTION (2.85 Å)