, Volume 18, Issue 4, pp 375–386 | Cite as

Molecular Dynamics Simulations of the Periplasmic Ferric-hydroxamate Binding Protein FhuD

  • Karla D. Krewulak
  • Craig M. Shepherd
  • Hans J. Vogel


FhuD is a periplasmic binding protein (PBP) that, under iron-limiting conditions, transports various hydroxamate-type siderophores from the outer membrane receptor (FhuA) to the inner membrane ATP-binding cassette transporter (FhuBC). Unlike many other PBPs, FhuD possesses two independently folded domains that are connected by an α-helix rather than two or three central β-strands. Crystal structures of FhuD with and without bound gallichrome have provided some insight into the mechanism of siderophore binding as well as suggested a potential mechanism for FhuD binding to FhuB. Since the α-helix connecting the two domains imposes greater rigidity on the structure relative to the β-strands in other ‘classical’ PBPs, these structures reveal no large conformational change upon binding a hydroxamate-type siderophore. Therefore, it is difficult to explain how the inner membrane transporter FhuB can distinguish between ferrichrome-bound and ferrichrome-free FhuD. In the current study, we have employed a 30 ns molecular dynamics simulation of FhuD with its bound siderophore removed to explore the dynamic behavior of FhuD in the substrate-free state. The MD simulation suggests that FhuD is somewhat dynamic with a C-terminal domain closure of 6° upon release of its siderophore. This relatively large motion suggests differences that would allow FhuB to distinguish between ferrichrome-bound and ferrichrome-free FhuD.

Key words

computer simulation iron molecular dynamics periplasm siderophore 


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Copyright information

© Springer 2005

Authors and Affiliations

  • Karla D. Krewulak
    • 1
  • Craig M. Shepherd
    • 1
    • 2
  • Hans J. Vogel
    • 1
  1. 1.Structural Biology Research Group, Department of Biological SciencesUniversity of CalgaryAlbertaCanada
  2. 2.The Scripps Research InstituteLa JollaU.S.A.

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