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A key role for the periplasmic PfeE esterase in iron acquisition via the siderophore Enterobactin in Pseudomonas aeruginosa

DOI: 10.1021/acschembio.8b00543 DOI Help

Authors: Quentin Perraud (Université de Strasbourg; CNRS) , Lucile Moynie (University of St Andrews; Research Complex at Harwell) , Véronique Gasser (Université de Strasbourg; CNRS) , Mathilde Munier (Université de Strasbourg; CNRS) , Julien Godet (Université de Strasbourg) , Françoise Hoegy (Université de Strasbourg; CNRS) , Yves Mély (Université de Strasbourg) , Gaëtan L. A. Mislin (5Université de Strasbourg) , James H. Naismith (University of St. Andrews; Research Complex at Harwell) , Isabelle J. Schalk (University of St Andrews; Research Complex at Harwell)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Chemical Biology

State: Published (Approved)
Published: August 2018

Abstract: Enterobactin (ENT) is a siderophore (iron-chelating compound) produced by Escherichia coli in order to gain access to iron, an essential nutriment for bacterial growth. ENT is used as an exosiderophore by the opportunistic human pathogen Pseudomonas aeruginosa with transport of ferri-ENT across the bacterial outer membrane by the transporter PfeA. Next to pfeA gene on the chromosome is localized a gene encoding for an esterase, PfeE, whose transcription is regulated, as for pfeA, by the presence of ENT in bacterial environment. Purified PfeE hydrolyzed ferri-ENT into three molecules of 2,3 DHBS (2,3 dihydroxybenzoylserine) still complexed with ferric iron, and complete dissociation of iron from ENT chelating groups was only possible in the presence of both PfeE and an iron reducer, such as DTT. The crystal structure of PfeE and an inactive PfeE mutant complexed with ferri-ENT or a non-hydrolysable ferri-catechol complex allowed identification of the enzyme binding site and the catalytic triad. Finally, cell fractionation and fluorescence microscopy showed periplasmic localization of PfeE in P. aeruginosa cells. Thus, the molecular mechanism of iron release from ENT in P. aeruginosa differs from that previously described in E. coli. In P. aeruginosa, siderophore hydrolysis occurs in the periplasm, with ENT never reaching the bacterial cytoplasm. In E. coli, ferri-ENT crosses the inner membrane via the ABC transporter FepBCD and ferri-ENT is hydrolyzed by the esterase Fes only once it is in the cytoplasm.

Subject Areas: Biology and Bio-materials, Chemistry

Instruments: I24-Microfocus Macromolecular Crystallography