Helicobacter pylori hydrogenase accessory protein HypA and urease accessory protein UreG compete with each other for UreE recognition

Background

The gastric pathogen Helicobacter pylori relies on nickel-containing urease and hydrogenase enzymes in order to colonize the host. Incorporation of Ni²⁺ into urease is essential for the function of the enzyme and requires the action of several accessory proteins, including the hydrogenase accessory proteins HypA and HypB and the urease accessory proteins UreE, UreF, UreG and UreH.

Methods

Optical biosensing methods (biolayer interferometry and plasmon surface resonance) were used to screen for interactions between HypA, HypB, UreE and UreG.

Results

Using both methods, affinity constants were found to be 5 nM and 13 nM for HypA–UreE and 8 μM and 14 μM for UreG-UreE. Neither Zn²⁺ nor Ni²⁺ had an effect on the kinetics or stability of the HypA–UreE complex. By contrast, addition of Zn²⁺, but not Ni²⁺, altered the kinetics and greatly increased the stability of the UreE–UreG complex, likely due in part to Zn²⁺-mediated oligomerization of UreE. Finally our results unambiguously show that HypA, UreE and UreG cannot form a heterotrimeric protein complex in vitro; instead, HypA and UreG compete with each other for UreE recognition.

General significance

Factors influencing the pathogen's nickel budget are important to understand pathogenesis and for future drug design.