In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 108, No. 5 ( 2011-02), p. 2112-2117
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.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.1012588108
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2011
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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