CLONING AND SEQUENCING OF A HAEMOPHILUS-DUCREYI FUR HOMOLOG

Iron regulation in a growing number of bacterial species is being attr ibuted to the presence of a fur (ferric uptake regulation) regulatory system. In the presence of iron, Fur acts as a classical negative regu lator, binding conserved sequences within the promoter of iron-repress ible genes and blocking transcription. Western blot analysis utilizing Escherichia coli Fur antisera detected a band of approximately 17 kDa in soluble extracts of Haemophilus ducreyi. Additionally, Southern bl ot hybridization of the H. ducreyi chromosome with a meningococcal fur probe indicated that H. ducreyi might contain a fur homolog. This put ative fur homolog was cloned into the E. coli vector pACYC184. This cl one was capable of repressing expression of a normally Fur-regulated l acZ fusion in the fur-background of E. coli strain H1780. The deduced amino acid sequence shows H ducreyi fur to be 54% identical and 73% si milar to E. coli fur, containing putative DNA-binding and metal-bindin g domains. These data demonstrate that H ducreyi has a functional fur system.