The membrane protein FeoB contains an intramolecular G protein essential for Fe(II) uptake in bacteria.
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.
Marlovits
Thomas C
TC
Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, P.O. Box 208024, New Haven, CT 06520-8024, USA.
Haase
Winfried
W
Herrmann
Christian
C
Aller
Stephen G
SG
Unger
Vinzenz M
VM
D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D001665:Binding Sites; D002384:Catalysis; D027682:Cation Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007501:Iron / Q000378:metabolism*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D027682:Cation Transport Proteins; D029968:Escherichia coli Proteins; C470580:FeoB protein, E coli; D008565:Membrane Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D007501:Iron; D019204:GTP-Binding Proteins