The Coordination Chemistry of Two Peptidic Models of NFeoB and Core CFeoB Regions of FeoB Protein: Complexes of Fe(II), Mn(II), and Zn(II)

Often necessary for efficient Fe(II) trafficking into bacterial cell, the Feo system is a vital transporter for many pathogenic bacteria and indispensable for proper development and survival in the host organism during infection. In this work, we present the metal-binding characteristics of the peptidic models of two putative Fe(II)-binding sites of <i>E. coli</i>FeoB: <b>L1</b> (Ac-₄₇₇IMRGEATPFVMELPVYHVPH₄₉₆-CONH₂) being a fragment of the Core CFeoB region located between the transmembrane helices and <b>L2 (</b>Ac-₃₈VERKEG₄₃-CONH₂), which represents the ExxE motif found within the NFeoB domain. With a variety of physicochemical methods, such as potentiometry, mass spectrometry, NMR, and EPR spectroscopy, we have determined the stability constants and metal-binding residues for the complexes of Fe(II), Mn(II), and Zn(II) with two ligands, <b>L1</b> and <b>L2</b>, acting as models for the Core CFeoB and ExxE motif. We compare their affinities toward the studied metal ions with the previously studied C-terminal part of the protein and discuss a possible role in metal trafficking by the whole protein.