This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Braun, V. Articles by Herrmann, C. Search for Related Content PubMed PubMed Citation Articles by Braun, V. Articles by Herrmann, C.

 Previous Article  |  Next Article 

Journal of Bacteriology, October 2007, p. 6913-6918, Vol. 189, No. 19
0021-9193/07/$08.00+0     doi:10.1128/JB.00884-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Docking of the Periplasmic FecB Binding Protein to the FecCD Transmembrane Proteins in the Ferric Citrate Transport System of Escherichia coli

Volkmar Braun^1,2* and Christina Herrmann²

Department of Protein Evolution, Max Planck Institute for Developmental Biology,¹ Department of Microbiology and Membrane Physiology, University of Tübingen, 72076 Tübingen, Germany²

Received 6 June 2007/ Accepted 17 July 2007

Citrate-mediated iron transport across the cytoplasmic membrane is catalyzed by an ABC transporter that consists of the periplasmic binding protein FecB, the transmembrane proteins FecC and FecD, and the ATPase FecE. Salt bridges between glutamate residues of the binding protein and arginine residues of the transmembrane proteins are predicted to mediate the positioning of the substrate-loaded binding protein on the transmembrane protein, based on the crystal structures of the ABC transporter for vitamin B₁₂, consisting of the BtuF binding protein and the BtuCD transmembrane proteins (E. L. Borths et al., Proc. Natl. Acad. Sci. USA 99:16642-16647, 2002). Here, we examined the role of the residues predicted to be involved in salt-bridge formation between FecB and FecCD by substituting these residues with alanine, cysteine, arginine, and glutamate and by analyzing the citrate-mediated iron transport of the mutants. Replacement of E93 in FecB with alanine [FecB(E93A)], cysteine, or arginine nearly abolished citrate-mediated iron transport. Mutation FecB(E222R) nearly eliminated transport, and FecB(E222A) and FecB(E222C) strongly reduced transport. FecD(R54C) and FecD(R51E) abolished transport, whereas other R-to-C mutations in putative interaction sites between FecCD and FecB substantially reduced transport. The introduced cysteine residues in FecB and FecCD also served to examine the formation of disulfide bridges in place of salt bridges between the binding protein and the transmembrane proteins. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis results suggest cross-linking of FecB(E93C) to FecD(R54C) and FecB(E222C) to FecC(R60C). The data are consistent with the proposal that FecB(E93) is contained in the region that binds to FecD and FecB(E222) in the region that binds to FecC.

---

* Corresponding author. Mailing address: Max Planck Institute for Developmental Biology, Department of Protein Evolution, Spemannstasse 35, 72076 Tübingen, Germany. Phone: (49) 7071 601 343. Fax: (49) 7071 601 300. E-mail: volkmar.braun{at}tuebingen.mpg.de

Published ahead of print on 27 July 2007.

---

Journal of Bacteriology, October 2007, p. 6913-6918, Vol. 189, No. 19
0021-9193/07/$08.00+0     doi:10.1128/JB.00884-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Brooijmans, R. J. W., de Vos, W. M., Hugenholtz, J. (2009). Lactobacillus plantarum WCFS1 Electron Transport Chains. Appl. Environ. Microbiol. 75: 3580-3585 [Abstract] [Full Text]  
• Kim, Y., Wang, X., Ma, Q., Zhang, X.-S., Wood, T. K. (2009). Toxin-Antitoxin Systems in Escherichia coli Influence Biofilm Formation through YjgK (TabA) and Fimbriae. J. Bacteriol. 191: 1258-1267 [Abstract] [Full Text]