CHAPTER 3: Channel Protein FhuA as a Promising Biomolecular Scaffold for Bioconjugates
Published:18 Aug 2015
L. Zhu, M. Arlt, H. Liu, M. Bocola, D. F. Sauer, S. Gotzen, ... U. Schwaneberg, in Bio-Synthetic Hybrid Materials and Bionanoparticles: A Biological Chemical Approach Towards Material Science, ed. A. Boker and P. van Rijn, The Royal Society of Chemistry, 2015, pp. 57-72.
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The ferric hydroxamate uptake protein component A, FhuA, is a large monomeric transmembrane protein. FhuA functions as a receptor for ferrichrome and the structurally closely related antibiotic albomycin. In addition to its biological importance, FhuA is a robust protein scaffold that can be genetically modified and is stable under a broad range of conditions. By removing the globular cork domain (deletion of amino acids 1–160), FhuA became a large passive diffusion channel (FhuA Δ1–160) with an inner diameter of about 2.0 nm. FhuA was reconstituted in liposomes and polymersomes for controlled compound release responding to reducing agents and UV light. FhuA was also re-engineered to increase its length, enlarge its diameter and harbour single functional groups (–SH and –NH2). FhuA Δ1–159 Ext with an increased hydrophobic region was generated and inserted more efficiently into polymer membranes. FhuA Δ1–159 Exp has an enlarged diameter and shows increased diffusion kinetics. The remarkable resistance of FhuA variants to organic solvents and high temperatures makes it suitable as a scaffold for accommodating hybrid catalysts to perform chemical reactions. By substituting the amino acid residues surrounding the coupling site in the interior of the FhuA channel, one can also optimize the accessibility of the coupling site and the enantioselectivity.