Identification and characterization of a high-affinity zinc uptake system in Neisseria gonorrhoeae

Abstract

A search of the gonococcal genome database using the known zinc-binding protein (znuA) sequences from Escherichia coli and Haemophilus influenzae identified an open reading frame encoding a putative gonococcal ZnuA. The consensus amino acid sequence of this open reading frame possessed a characteristic 30-amino acid histidine-rich metal-binding motif (repetitive HDH sequence) containing 43% histidine and 37% aspartic acid and glutamic acid. Subsequently, two adjacent open reading frames with homology to E. coli and H. influenzae znuB and znuC were located upstream of znuA. When partially purified from sonicated cell-free supernatants by CMSepharose chromatography, the mature gonococcal ZnuA had an estimated molecular mass of 38 kDa by SDS^PAGE. The presence of a DNA sequence encoding a 19-amino acid signal peptide and the solubility of the mature ZnuA suggested that this protein was located in the periplasm. Inactivation of the Neisseria gonorrhoeae F62 znuA by insertional mutagenesis resulted in a mutant that had a growth rate lower than that of the wild-type parent strain and that required high concentrations of ZnCl 2 (v200 WM) for optimal growth. Using a chemically defined agar medium, the gonococcal ZnuA mutant grew only in the presence of Zn 2 , whereas Mg

A Strain-Specific Catalase Mutation and Mutation of the Metal-Binding Transporter Gene mntC Attenuate Neisseria gonorrhoeae In Vivo but Not by Increasing Susceptibility to Oxidative Killing by Phagocytes

“…Unfortunately we have been unable to introduce a wild-type copy of the mntC gene into the mutants GP304 and GP318, and therefore we have not definitively confirmed that the disadvantage shown in vivo is due to the absence of MntC. An impaired capacity to transport manganese and zinc (7,28) through the MntABC system may impose an in vivo growth defect to the mntC mutant, since such metals may be needed as cofactors for enzymes that are important for gonococcal survival in vivo. We did not observe a difference in growth between wild-type FA1090 and the mutants that lack mntC when cultured in GCB or on GC agar.…”

High-Affinity Zn2+Uptake System ZnuABC Is Required for Bacterial Zinc Homeostasis in Intracellular Environments and Contributes to the Virulence ofSalmonella enterica

“…A few investigations carried out in recent years with different bacteria have suggested an important role for the ZnuABC Zn 2ϩ uptake system for growth in environments poor in zinc and for virulence of gram-negative pathogens (7,9,22,27,28,30,33,52). These studies, however, have not analyzed the molecular bases of the contribution of ZnuABC to bacterial virulence.…”

“…Genetic and biochemical studies have shown that ZnuABC expression is repressed in cells containing adequate concentrations of zinc by the metallated form of Zur, a metalloregulatory DNA-binding protein with femtomolar sensitivity to free intracellular zinc (36,37,39). A few investigations carried out with different bacterial species have suggested that the integrity of the znuABC operon is essential to ensure the ability of different bacteria (Haemophilus influenzae, Haemophilus ducreyi, Brucella abortus, Pasteurella multocida, Neisseria gonorrhoeae, Salmonella enterica serovar Typhimurium) to grow in media devoid of zinc or within the infected host (7,9,22,27,28,30,33,52). These observations suggest that the amount of metals available for bacterial growth within the infected animal is limited, analogous to what is known for iron.…”

Neisserial TonB-dependent outer-membrane proteins: detection, regulation and distribution of three putative candidates identified from the genome sequences The GenBank accession number for the sequence of tdfH from meningococcal strain IR1074 reported in this paper is AF227418.

“…Recently a zinc transporter system (ZnuABC) has been described for E. coli and Haemophilus ducreyi (Lewis et al, 1999 ;Patzer & Hantke, 1998). Similarly, zinc periplasmic transporters are likely to be present in the gonococci (Chen & Morse, 2000) and meningococci. Further work is currently being undertaken to establish the functional role of TdfH and these putative transporter proteins among pathogenic neisseriae and other mucosal pathogens.…”