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The plug domain of a neisserial TonB‐dependent transporter retains structural integrity in the absence of its transmembrane β‐barrel
Author(s) -
Oke M,
Sarra R,
Ghirlando R,
Farnaud S,
Gorringe A.R,
Evans R.W,
Buchanan S.K
Publication year - 2004
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(04)00196-6
Subject(s) - bacterial outer membrane , periplasmic space , isothermal titration calorimetry , transferrin , transmembrane protein , transmembrane domain , biochemistry , chemistry , biophysics , escherichia coli , biology , membrane , receptor , gene
Transferrin binding protein A (TbpA) is a TonB‐dependent outer membrane protein expressed by pathogenic bacteria for iron acquisition from human transferrin. The N‐terminal 160 residues (plug domain) of TbpA were overexpressed in both the periplasm and cytoplasm of Escherichia coli . We found this domain to be soluble and monodisperse in solution, exhibiting secondary structure elements found in plug domains of structurally characterized TonB‐dependent transporters. Although the TbpA plug domain is apparently correctly folded, we were not able to observe an interaction with human transferrin by isothermal titration calorimetry or nitrocellulose binding assays. These experiments suggest that the plug domain may fold independently of the β‐barrel, but extracellular loops of the β‐barrel are required for ligand binding.