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

Abstract

It was shown that feuB mutants (defective in ferric enterochelin uptake) were unable to adsorb colicin B. In addition, they were missing one of the 3 outer membrane proteins which are overproduced in strains grown in iron deficient, extracted medium. Thus, this protein (the feuB protein) is probably the receptor for colicin B and functions in enterochelin mediated iron transport. The feuB gene was located by P1 transduction at approximately 72.5 min on the E. coli K12 genetic map and thus 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 iron uptake system is discussed.