The membrane protein FeoB contains an intramolecular G protein essential for Fe(II) uptake in bacteria

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 membranespanning 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 guaninenucleotide-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 GTPbound 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.

The sensor kinase PhoQ mediates virulence in Pseudomonas aeruginosa

“…FeoAB is a well-conserved system that is involved in the transport of ferrous iron (Marlovits et al, 2002). Previous studies have shown that FeoB mutants of Escherichia coli (Boyer et al, 2002;Kammler et al, 1993) and Helicobacter pylori (Velayudhan et al, 2000) demonstrate reduced virulence and/or colonization activity, yet in our study the equivalent P. aeruginosa mutants demonstrated normal wild-type virulence in rat chronic lung infections (data not shown).…”

Potassium-activated GTPase Reaction in the G Protein-coupled Ferrous Iron Transporter B

“…This indicated that the Switch I region was not essential for nucleotide or Mg 2ϩ binding, consistent with mutational analysis of conserved residues in Switch I of E. coli FeoB, which did not significantly affect its GTPase activity (8). Conversely, studies upon full-length FeoB harboring the same mutations in Switch I were unable to restore Fe 2ϩ uptake in a feoB-deficient background (6). This apparent disparity has left the role played by the Switch I region in FeoB open.…”

“…The prokaryotic G protein-coupled ferrous iron (Fe 2ϩ ) transporter B (FeoB) is unique in that its cytoplasmic G protein domain is directly tethered to a polytopic membrane domain (6). The G protein domain belongs to the TrmE-Era-EngAYihA-Septin-like (TEES) 4 superfamily of bacterial GTPases, which are recognized by sequence conservation between the G 1 and G 2 motifs.…”

“…GTP binding to the G protein domain (FeoGP) initiates the transport of Fe 2ϩ across the membrane, which is halted by the hydrolysis of GTP to GDP. Previous studies have shown that FeoGP has slow GTPase activity (Escherichia coli k cat ϭ 0.0015 s Ϫ1 , equivalent to the hydrolysis of one GTP molecule in 11 min) (6,8,9). A slow intrinsic GTPase rate is not uncommon for G proteins, because their activity can be accelerated by GTPase-activating proteins (GAPs), which can stimulate GTP hydrolysis by several orders of magnitude (10).…”

Rapid selective sweep of pre-existing polymorphisms and slow fixation of new mutations in experimental evolution of Desulfovibrio vulgaris

“…Different alleles of DVU2571 or DVU2287 were identified in stressevolved ES8 and ES9 and non-stress-evolved EC3 (Figure 1, Table 1, Supplementary Figure S3). DVU2571 encodes a ferrous iron transport protein FeoB that functions as an Fe 2+ permease (Marlovits et al, 2002;Cartron et al, 2006). Mutations in iron acquisition-related genes were identified in saltadapted or butanol-adapted E. coli (Dragosits et al, 2013) as well as being up-expressed genes when exposed to various stresses, in statoinary-phase cells or biofilm populations in DvH (Clark et al, 2006(Clark et al, , 2012Zhou et al, 2011).…”