PMID: 23104801

Authors:

Lau CK, Ishida H, Liu Z, Vogel HJ

Title:

Solution structure of Escherichia coli FeoA and its potential role in bacterial ferrous iron transport.

Journal:

J Bacteriol. 2012 Oct 26.

Abstract:

Iron is an indispensible nutrient for most organisms. Ferric iron (Fe(3+)) predominates under aerobic conditions, while during oxygen limitation ferrous (Fe(2+)) iron is usually present. The Feo system is a bacterial ferrous iron transport system first discovered in Escherichia coli K12. It consists of three genes, feoA, feoB, and feoC (yhgG). FeoB is thought to be the main transmembrane transporter while FeoC is considered to be a transcriptional regulator. Using multidimensional Nuclear Magnetic Resonance (NMR) spectroscopy, we have determined the solution structure of E. coli FeoA. The structure of FeoA reveals a Src-Homology 3 (SH3)-like fold. The structure is composed of a beta-barrel with two alpha-helices where one helix is positioned over the barrel. In comparison to the standard eukaryotic SH3 fold, FeoA has two additional alpha-helices. FeoA was further characterized by heteronuclear NMR dynamics measurements, which suggests that it is a monomeric stable globular protein. Model free analysis of the NMR relaxation results indicates that a slow conformational dynamic process is occurring in beta-strand 4 that may be important for function. (31)P NMR based GTPase activity measurements with the N-terminal domain of FeoB (NFeoB) indicate a higher GTP hydrolysis rate in the presence of potassium versus sodium. Further enzymatic assays with NFeoB suggest that FeoA may not act as a GTPase Activating Protein as previously proposed. These findings together with bioinformatics and structural analyses suggest that FeoA may have a different role, possibly interacting with the cytoplasmic domain of the highly conserved core portion of the FeoB transmembrane region.