Hydrogenase activity in the foodborne pathogen Campylobacter jejuni depends upon a novel ABC-type nickel transporter (NikZYXWV) and is SlyD-independent

Abstract

Campylobacter jejuni is a human pathogen of worldwide significance. It is commensal in the gut of many birds and mammals, where hydrogen is a readily available electron donor. The bacterium possesses a single membrane-bound, periplasmic-facing NiFe uptake hydrogenase that depends on the acquisition of environmental nickel for activity. The periplasmic binding protein Cj1584 (NikZ) of the ATP binding cassette (ABC) transporter encoded by the cj1584c-cj1580c (nikZYXWV) operon in C. jejuni strain NCTC 11168 was found to be nickel-repressed and to bind free nickel ions with a submicromolar K d value, as measured by fluorescence spectroscopy. Unlike the Escherichia coli NikA protein, NikZ did not bind EDTA-chelated nickel and lacks key conserved residues implicated in metallophore interaction. A C. jejuni cj1584c null mutant strain showed an approximately 22-fold decrease in intracellular nickel content compared with the wildtype strain and a decreased rate of uptake of 63 NiCl 2 . The inhibition of residual nickel uptake at higher nickel concentrations in this mutant by hexa-ammine cobalt (III) chloride or magnesium ions suggests that low-affinity uptake occurs partly through the CorA magnesium transporter. Hydrogenase activity was completely abolished in the cj1584c mutant after growth in unsupplemented media, but was fully restored after growth with 0.5 mM nickel chloride. Mutation of the putative metallochaperone gene slyD (cj0115) had no effect on either intracellular nickel accumulation or hydrogenase activity. Our data reveal a strict dependence of hydrogenase activity in C. jejuni on high-affinity nickel uptake through an ABC transporter that has distinct properties compared with the E. coli Nik system.

Defining the metabolic requirements for the growth and colonization capacity of Campylobacter jejuni

“…The accessory factors encoded by the hypFBCDEA operon ( cj0622-cj0627 ) are required for assembling of the hydrogenase enzyme complex and insertion of the nickel cofactor. An ABC-transporter system (Cj1584c-Cj1580c) of C. jejuni NCTC 11168 has recently been identified as a high-affinity nickel uptake system and was named NikZYXWV (Howlett et al, 2012). Under low nickel concentrations the inactivation of nikZ ( cj1584c ), encoding for a periplasmic binding protein, led to an abolished hydrogenase activity of the mutant strain.…”

“…This result demonstrated the importance of the Nik-transporter system for the acquisition of nickel as a cofactor for the enzyme. Yet hydrogenase activity of the nik Z mutant was observed in the presence of high nickel concentrations, indicating the presence of additional nickel transporters (Howlett et al, 2012). In contrast to studies with E. coli , showing the importance of the nickel chaperone SlyD for the hydrogenase activity, a mutation in the slyD ortholog gene cj0115 of C. jejuni NCTC 11168 did not abolish the mutants nickel uptake capacity and hydrogenase activity (Howlett et al, 2012).…”

Characterization in Helicobacter pylori of a Nickel Transporter Essential for Colonization That Was Acquired during Evolution by Gastric Helicobacter Species

“…coli [32], is composed of NikA, a periplasmic binding protein, NikBC, two integral membrane components, and NikDE, two ATPases that energize substrate translocation through ATP hydrolysis. Another nickel ABC transporter has been identified in Campylobacter jejuni , that is composed of NikZYXWV [33,34]. In S .…”

It takes two to tango: two TatA paralogues and two redox enzyme-specific chaperones are involved in the localization of twin-arginine translocase substrates in Campylobacter jejuni

“…For example, DnaK is involved in TAT targeting of the E. coli multi-copper oxidase CueO (Graubner et al , 2007) and SlyD is necessary for assembly of hydrogenases in E. coli (Zhang et al , 2005), although we found this was not the case in C. jejuni (Howlett et al , 2012). In fact in C. jejuni , only two obvious REMPs are encoded in the genome (Turner et al , 2004), FdhM (Cj1514) and Cj0785.…”