Iron‐hydroxamate uptake systems inBacillus subtilis: identification of a lipoprotein as part of a binding protein‐dependent transport system

摘要

SummaryBacillus subtiliswas shown to utilize three types of hydroxamate siderophores, ferrichromes, ferrioxamines and shizokinen, each of which is taken up by different transport systems. Mutants deficient in the uptake of ferrichrome and/or ferrioxamine B were isolated. The genefhuD, which was able to complement a mutant defective in ferrichrome uptake, was cloned. The deduced sequence of FhuD showed low but significant homology to the binding proteins FepB, FecB and FhuD ofEscherichia coli, which are all components of binding protein‐dependent, ferric siderophore transport systems. The first 23 amino acids of FhuD ofB. subtilispossessed all characteristics of a lipoprotein signal sequence. The processing of FhuD inE. coliwas inhibited by globomycin. Inhibition by globomycin indicated a lipid modification at theN‐terminal cysteine inE. coli.It is highly likely that this step may also take place inB. subtilis.As in other binding protein‐dependent transport systems of Gram‐positive organisms it is proposed that the lack of a periplasm is compensated for by the lipid through which the binding protein is anchored to the cytoplasmic m