Identification of the znuA -Encoded Periplasmic Zinc Transport Protein of Haemophilus ducreyi

Abstract

ABSTRACT The znuA gene of Haemophilus ducreyi encodes a 32-kDa (mature) protein that has homology to both the ZnuA protein of Escherichia coli and the Pzp1 protein of H. influenzae ; both of these latter proteins are members of a growing family of prokaryotic zinc transporters. Inactivation of the H. ducreyi 35000 znuA gene by insertional mutagenesis resulted in a mutant that grew more slowly than the wild-type parent strain in vitro unless ZnCl 2 was provided at a final concentration of 100 μM. Other cations tested did not restore growth of this H. ducreyi mutant to wild-type levels. The H. ducreyi ZnuA protein was localized to the periplasm, where it is believed to function as the binding component of a zinc transport system. Complementation of the znuA mutation with the wild-type H. ducreyi znuA gene provided in trans restored the ability of this H. ducreyi mutant to grow normally in the absence of exogenously added ZnCl 2 . The wild-type H. ducreyi znuA gene was also able to complement a H. influenzae pzp1 mutation. The H. ducreyi znuA isogenic mutant exhibited significantly decreased virulence ( P = 0.0001) when tested in the temperature-dependent rabbit model for experimental chancroid. This decreased virulence was not observed when the znuA mutant was complemented with the wild-type H. ducreyi znuA gene provided in trans .