PMID:12446835

Citation	Marlovits, TC, Haase, W, Herrmann, C, Aller, SG and Unger, VM (2002) The membrane protein FeoB contains an intramolecular G protein essential for Fe(II) uptake in bacteria. Proc. Natl. Acad. Sci. U.S.A. 99:16243-8
Abstract	G proteins are critical for the regulation of membrane protein function and signal transduction. Nevertheless, coupling between G proteins and membrane proteins with multiple membrane-spanning domains has so far been observed only in higher organisms. Here we show that the polytopic membrane protein FeoB, which is essential for Fe(II) uptake in bacteria, contains a guanine-nucleotide-specific nucleotide binding site. We identify the G4-motif, NXXD, responsible for guanine nucleotide specificity, and show that GTP hydrolysis occurs very slowly. In contrast to typical G proteins, the association and dissociation of GDP were found to be faster than for GTP, suggesting that in the absence of additional factors, FeoB's G protein domain may exist mostly in the GTP-bound form. Furthermore, the binding of GTP is required for efficient Fe(II) uptake through the FeoB-dependent system. Notably, even in bacteria, this covalent linkage between a G protein and a polytopic membrane protein appears, to our knowledge, to be unique. These findings raise the intriguing question whether FeoB represents a primordial archetype of G protein-regulated membrane proteins.
Links	PubMed PMC138596 Online version:10.1073/pnas.242338299
Keywords	Adenosine Triphosphate/metabolism; Amino Acid Motifs; Binding Sites; Catalysis; Cation Transport Proteins/chemistry; Cation Transport Proteins/genetics; Cation Transport Proteins/metabolism; Escherichia coli/genetics; Escherichia coli/metabolism; Escherichia coli Proteins/chemistry; Escherichia coli Proteins/genetics; Escherichia coli Proteins/metabolism; Evolution, Molecular; GTP-Binding Proteins/chemistry; GTP-Binding Proteins/genetics; GTP-Binding Proteins/metabolism; Guanosine Diphosphate/metabolism; Guanosine Triphosphate/metabolism; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Iron/metabolism; Membrane Proteins/chemistry; Membrane Proteins/genetics; Membrane Proteins/metabolism; Protein Structure, Tertiary; Structure-Activity Relationship; Substrate Specificity
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