PDBsum entry 2grx

Metal transport

PDB id: 2grx

Contents

Protein chains

702 a.a.

78 a.a.

Ligands

GCN-GCN-KDO-KDO-GMH ×2

PO4 ×2

FTT ×8

DPO ×2

DAO ×2

EAP ×2

FCI ×2

MYR

References listed in PDB file

Key reference

Title

Structure of tonb in complex with fhua, E. Coli outer membrane receptor.

Authors

P.D.Pawelek, N.Croteau, C.Ng-Thow-Hing, C.M.Khursigara, N.Moiseeva, M.Allaire, J.W.Coulton.

Ref.

Science, 2006, 312, 1399-1402. [DOI no: 10.1126/science.1128057]

PubMed id

16741125

Abstract

The cytoplasmic membrane protein TonB spans the periplasm of the Gram-negative bacterial cell envelope, contacts cognate outer membrane receptors, and facilitates siderophore transport. The outer membrane receptor FhuA from Escherichia coli mediates TonB-dependent import of ferrichrome. We report the 3.3 angstrom resolution crystal structure of the TonB carboxyl-terminal domain in complex with FhuA. TonB contacts stabilize FhuA's amino-terminal residues, including those of the consensus Ton box sequence that form an interprotein beta sheet with TonB through strand exchange. The highly conserved TonB residue arginine-166 is oriented to form multiple contacts with the FhuA cork, the globular domain enclosed by the beta barrel.

Figure 1.
Fig. 1. Overall structure of the TonB-FhuA complex. (A) Cartoon representation of TonB residues 158 to 235 complexed to FhuA. ß strands are indicated as flat arrows; helices are indicated as flat coils. View is along a plane parallel to the OM. Horizontal bars delineate approximate OM boundaries. Arrow indicates direction toward periplasm. TonB is bound at the periplasmic face of FhuA. The FhuA cork domain (residues 19 to 160) is colored green; remaining residues (8 to 18; 161 to 725) are colored blue. TonB residues are colored yellow. (B) View of the TonB-FhuA complex along the longitudinal axis of the FhuA barrel, looking down on the periplasm-exposed surface of the complex. TonB secondary-structure elements ( 1, 2, ß1, ß2, ß3) are labeled. FhuA periplasmic turns 1, and 7 to 10 (T1, T7, T8, T9, T10), are also labeled for reference. (C) Electron density (blue) from a simulated-annealing composite omit 2F[obs] - F[calc] electron density map contoured at 1 showing the extension of electron density from FhuA Ile^9 to Gln18. FhuA residues between 8 and 18 are shown as sticks and colored by atom (carbon, white; nitrogen, blue; oxygen, red). FhuA cork domain residues (19 to 160) are shown as a green coil. FhuA barrel domain residues (161 to 725) are shown as a blue coil. TonB is shown as a yellow coil. TonB helices 1 and 2 are labeled for reference.

Figure 3.
Fig. 3. Residues from the FhuA cork and barrel domains interacting with TonB Arg166. Cut-away view showing FhuA and TonB protomers in cartoon representation; ß strands are shown as flat arrows, helices as flat coils. The FhuA cork domain (residues 19 to 160) is colored green; the remaining FhuA residues are colored blue. TonB is colored yellow. TonB Arg166 and interacting FhuA residues (Ala^26, Glu56, Ala^591, and Asn594) are shown as sticks colored by atoms (as in Fig. 1C). Strands of the central ß sheet of the FhuA cork domain (ß1 to ß4) are labeled.

The above figures are reprinted by permission from the AAAs: Science (2006, 312, 1399-1402) copyright 2006.