Premium
TonB‐dependent iron acquisition: mechanisms of siderophore‐mediated active transport †
Author(s) -
Moeck Gregory S.,
Coulton James W.
Publication year - 1998
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.1998.00817.x
Subject(s) - periplasmic space , bacterial outer membrane , siderophore , chemiosmosis , biology , biophysics , cytoplasm , ligand (biochemistry) , receptor , membrane , microbiology and biotechnology , cell membrane , biochemistry , inner membrane , escherichia coli , atp synthase , gene , enzyme
Cells growing in aerobic environments have developed intricate strategies to overcome the scarcity of iron, an essential nutrient. In Gram‐negative bacteria, high‐affinity iron acquisition requires outer membrane‐localized proteins that bind iron chelates at the cell surface and promote their uptake. Transport of bound chelates across the outer membrane depends upon TonB–ExbB–ExbD, a cytoplasmic membrane‐localized complex that transduces energy from the proton motive force to high‐affinity receptors in the outer membrane. Upon ligand binding to iron chelate receptors, conformational changes are induced, some of which are detected in the periplasm. These structural alterations signal the ligand‐loaded status of the receptor and, therefore, the requirement for TonB‐dependent energy transduction. Thus, TonB interacts preferentially and directly with ligand‐loaded receptors. Such a mechanism ensures the productive use of cellular energy to drive active transport at the outer membrane.