1TQQ

Structure of TolC in complex with hexamminecobalt

1TQQ の概要

• エントリーDOI: 10.2210/pdb1tqq/pdb
• 分子名称: Outer membrane protein tolC, COBALT HEXAMMINE(III) (3 entities in total)
• 機能のキーワード: beta-barrel, alpha-barrel, transport protein
• 由来する生物種: Escherichia coli
• 細胞内の位置: Cell outer membrane; Multi-pass membrane protein: P02930
• タンパク質・核酸の鎖数: 3
• 化学式量合計: 154689.86

構造登録者

Higgins, M.K.,Eswaran, J.,Edwards, P.C.,Schertler, G.F.,Hughes, C.,Koronakis, V. (登録日: 2004-06-18, 公開日: 2004-07-20, 最終更新日: 2023-08-23)

主引用文献

Higgins, M.K.,Eswaran, J.,Edwards, P.C.,Schertler, G.F.,Hughes, C.,Koronakis, V.
Structure of the ligand-blocked periplasmic entrance of the bacterial multidrug effllux protein TolC
J.Mol.Biol., 342:697-702, 2004

PubMed Abstract: The trimeric TolC protein of Escherichia coli comprises an outer membrane beta-barrel and a contiguous alpha-helical barrel projecting across the periplasm. This provides a single 140 A long pore for multidrug efflux and protein export. We have previously reported that trivalent cations such as hexammine cobalt can severely inhibit the conductivity of the TolC pore reconstituted in planar lipid bilayers. Here, isothermal calorimetry shows that Co(NH(3))(6)(3+) binds to TolC with an affinity of 20 nM. The crystal structure of the TolC-Co(NH(3))(6)(3+) complex was determined to 2.75 A resolution, and showed no significant difference in the protein when compared with unliganded TolC. An electron density difference map revealed that a single ligand molecule binds at the centre of the periplasmic entrance, the sole constriction of TolC. The octahedral symmetry of the ligand and the three-fold rotational symmetry of the TolC entrance determine a binding site in which the ligand forms hydrogen bonds with the Asp(374) residue of each monomer. When Asp(374) was substituted by alanine, high affinity ligand binding was abolished and inhibition of TolC pore conductivity in lipid bilayers was alleviated. Comparable effects followed independent substitution of the neighbouring Asp(371), indicating that this aspartate ring also contributes to the high affinity ligand binding site. As the electronegative entrance is widely conserved in the TolC family, it may be a useful target for the development of inhibitors against multidrug resistant pathogenic bacteria.

PubMed: 15342230
DOI: 10.1016/j.jmb.2004.07.088

実験手法

X-RAY DIFFRACTION (2.75 Å)