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Conjuring up a ghost: structural and functional characterization of FhuF, a ferric siderophore reductase from E. coli

DOI: 10.1007/s00775-021-01854-y DOI Help

Authors: I. B. Trindade (Universidade Nova de Lisboa) , G. Hernandez (Universidade Nova de Lisboa) , E. Lebègue (Université de Nantes, CNRS) , F. Barrière (Université Rennes, CNRS) , T. Cordeiro (Universidade Nova de Lisboa) , M. Piccioli (University of Florence; Consorzio Interuniversitario Risonanze Magnetiche di Metallo Proteine (CIRMMP)) , R. O. Louro (Universidade Nova de Lisboa)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Jbic Journal Of Biological Inorganic Chemistry , VOL 361

State: Published (Approved)
Published: February 2021
Diamond Proposal Number(s): 20161

Open Access Open Access

Abstract: Iron is a fundamental element for virtually all forms of life. Despite its abundance, its bioavailability is limited, and thus, microbes developed siderophores, small molecules, which are synthesized inside the cell and then released outside for iron scavenging. Once inside the cell, iron removal does not occur spontaneously, instead this process is mediated by siderophore-interacting proteins (SIP) and/or by ferric-siderophore reductases (FSR). In the past two decades, representatives of the SIP subfamily have been structurally and biochemically characterized; however, the same was not achieved for the FSR subfamily. Here, we initiate the structural and functional characterization of FhuF, the first and only FSR ever isolated. FhuF is a globular monomeric protein mainly composed by α-helices sheltering internal cavities in a fold resembling the “palm” domain found in siderophore biosynthetic enzymes. Paramagnetic NMR spectroscopy revealed that the core of the cluster has electronic properties in line with those of previously characterized 2Fe–2S ferredoxins and differences appear to be confined to the coordination of Fe(III) in the reduced protein. In particular, the two cysteines coordinating this iron appear to have substantially different bond strengths. In similarity with the proteins from the SIP subfamily, FhuF binds both the iron-loaded and the apo forms of ferrichrome in the micromolar range and cyclic voltammetry reveals the presence of redox-Bohr effect, which broadens the range of ferric-siderophore substrates that can be thermodynamically accessible for reduction. This study suggests that despite the structural differences between FSR and SIP proteins, mechanistic similarities exist between the two classes of proteins.

Journal Keywords: Ferric-siderophore reductase; Iron uptake; 2Fe–2S protein; Redox-Bohr effect

Subject Areas: Chemistry, Biology and Bio-materials

Instruments: B21-High Throughput SAXS

Added On: 10/02/2021 16:42


Discipline Tags:

Biochemistry Chemistry Structural biology Inorganic Chemistry Life Sciences & Biotech

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS)