Iron transport of Escherichia coli K-12: involvement of the colicin B receptor and of a citrate-inducible protein

Abstract

The feuB mutants [of E. coli] (defective in ferric enterochelin uptake) were unable to adsorb colicin B. They were also missing 1 of the 3 outer-membrane proteins which are overproduced in strains grown in Fe-deficient, extracted medium. This protein (the feuB protein) is probably the receptor for colicin B and functions in enterochelin-mediated Fe transport. The feuB gene was located by [phage] P1 transduction at .apprx. 72.5 min on the E. coli K-12 genetic map and maps separately from the other genes concerned with the enterochelin system. The outer membranes of various strains grown in the presence of 1 mM citrate contained a high level of a protein which was present in very small amounts when citrate was absent from the growth medium. This protein was most easily observed in feuB mutants grown in the presence of citrate, since on polyacrylamide gels it ran in a similar position to the feuB protein, which is missing in these mutants. The relationship of this citrate-inducible protein to the inducible citrate-dependent Fe uptake system is discussed.