5ADV: The Periplasmic Binding Protein Ceue Of Campylobacter Jejuni Preferentially Binds The Iron(iii) Complex Of The Linear Dimer Component Of Enterobactin

Citation:
Abstract
To acquire essential Fe(III), bacteria produce and secrete siderophores with high affinity and selectivity for Fe(III) to mediate its uptake into the cell. Here, we show that the periplasmic binding protein CeuE of Campylobacter jejuni, which was previously thought to bind the Fe(III) complex of the hexadentate siderophore enterobactin (Kd approximately 0.4 +/- 0.1 microM), preferentially binds the Fe(III) complex of the tetradentate enterobactin hydrolysis product bis(2,3-dihydroxybenzoyl-l-Ser) (H5-bisDHBS) (Kd = 10.1 +/- 3.8 nM). The protein selects Lambda-configured [Fe(bisDHBS)](2-) from a pool of diastereomeric Fe(III)-bisDHBS species that includes complexes with metal-to-ligand ratios of 1:1 and 2:3. Cocrystal structures show that, in addition to electrostatic interactions and hydrogen bonding, [Fe(bisDHBS)](2-) binds through coordination of His227 and Tyr288 to the iron center. Similar binding is observed for the Fe(III) complex of the bidentate hydrolysis product 2,3-dihydroxybenzoyl-l-Ser, [Fe(monoDHBS)2](3-) The mutation of His227 and Tyr288 to noncoordinating residues (H227L/Y288F) resulted in a substantial loss of affinity for [Fe(bisDHBS)](2-) (Kd approximately 0.5 +/- 0.2 microM). These results suggest a previously unidentified role for CeuE within the Fe(III) uptake system of C. jejuni, provide a molecular-level understanding of the underlying binding pocket adaptations, and rationalize reports on the use of enterobactin hydrolysis products by C. jejuni, Vibrio cholerae, and other bacteria with homologous periplasmic binding proteins.
PDB ID: 5ADVDownload
MMDB ID: 139466
PDB Deposition Date: 2015/8/24
Updated in MMDB: 2016/06
Experimental Method:
x-ray diffraction
Resolution: 2.1  Å
Source Organism:
Similar Structures:
Biological Unit for 5ADV: monomeric; determined by author and by software (PISA)
Molecular Components in 5ADV
Label Count Molecule
Protein (1 molecule)
1
Enterochelin Uptake Periplasmic Binding Protein
Molecule annotation
Chemicals (5 molecules)
1
1
2
2
3
2
* Click molecule labels to explore molecular sequence information.

Citing MMDB
.