Bacteria in an intense competition for iron: Key component of the Campylobacter jejuni iron uptake system scavenges enterobactin hydrolysis product

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 ∼ 0.4 ± 0.1 µM), 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 Λ-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 ∼ 0.5 ± 0.2 µM). 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.

Interactions of the periplasmic binding protein CeuE with Fe(III) n-LICAM4− siderophore analogues of varied linker length

“…Fluorescence quenching studies with CeuE were carried out on a Hitachi F-4500 fluorescence spectrophotometer as previously reported22.…”

“…The octahedral coordination of the Fe(III) ion was completed by two protein residues, Tyr288 and His227. Subsequent studies22 showed that 4-LICAM 4− was a good mimic of the natural tetradentate linear enterobactin hydrolysis product: bis(2,3-dihydroxybenzoyl-L-Ser) ( PDB ID: 5ADV, 5ADW ), (Fig. 1).…”

Chemische und biologische Aspekte von “Nutritional Immunity” – Perspektiven für neue Antiinfektiva mit Fokus auf bakterielle Eisenaufnahmesysteme

“…Wettkampf um Eisen 3.4.1. [75] Dieser Ansatz unterscheidet sich deutlich von der üblicheren Fe 3+ -Aufnahme durch sechszähnige Siderophore. So wurden bei der Untersuchung von cokultivierten Umweltbakterien Isolate entdeckt, deren Wachstum vollständig von benachbarten Bakterien abhängig war.…”

“…Strukturelle und biophysikalische Studien an Campylobacter jejuni,e inem Organismus,d er keine eigenen Siderophore bilden kann, zeigten, wie CeuE, ein periplasmatisches Siderophor-Bindeprotein, von anderen Bakterien erzeugte Enterobactin-Hydrolyseprodukte mit hoher Affinitätbinden kann. [75] Dieser Ansatz unterscheidet sich deutlich von der üblicheren Fe 3+ -Aufnahme durch sechszähnige Siderophore.…”

A mathematical model of Campylobacter dynamics within a broiler flock

“…Competition for resources is the key to 85 success within the gut. Campylobacter is known to be an effective coloniser [22], as it is 86 very effective at drawing zinc [23] and iron [24] from its environment. The second term 87 (γCP ) in equation (1) models the inhibitory effect of host defence peptides, P .…”