A multifunctional ATP-binding cassette transporter system from Vibrio cholerae transports vibriobactin and enterobactin

Vibrio cholerae uses the catechol siderophore vibriobactin for iron transpo rt under iron-limiting conditions. We have identified genes for vibriobacti n transport and mapped them within the vibriobactin biosynthetic gene clust er. Within this genetic region we have identified four genes, viuP, viuD, v iuG and viuC, whose protein products have homology to the periplasmic bindi ng protein, the two integral cytoplasmic membrane proteins, and the ATPase component, respectively, of other iron transport systems, The amino-termina l region of ViuP has homology to a lipoprotein signal sequence, and ViuP co uld be labeled with [H-3] palmitic acid. This suggests that ViuP is a membr ane lipoprotein. The ViuPDGC system transports both vibriobactin and entero bactin in Escherichia coli. In the same assay, the E. coli enterobactin tra nsport system, FepBDGC, allowed the utilization of enterobactin but not vib riobactin, Although the entire viuPDGC system could complement mutations in fepB, fepD,fepG, or fepC only viuC was able to independently complement th e corresponding fep mutation. This indicates that these proteins usually fu nction as a complex. V. cholerae strains carrying a mutation in viuP or in, in viuG were constructed by marker exchange. These mutations reduced, but d id not completely eliminate, vibriobactin utilization. This suggests that V . cholerae contains genes in addition to viuPDGC that function in the trans port of catechol siderophores.