Crystal Structures of Apo and Metal-Bound Forms of the UreE Protein from Helicobacter pylori: Role of Multiple Metal Binding Sites,

Abstract

Received March 10, 2010; Revised Manuscript Received July 15, 2010 ABSTRACT: The crystal structure of the urease maturation protein UreE from Helicobacter pylori has been determined in its apo form at 2.1 Å resolution, bound to Cu 2þ at 2.7 Å resolution, and bound to Ni 2þ at 3.1 Å resolution. Apo UreE forms dimers, while the metal-bound enzymes are arranged as tetramers that consist of a dimer of dimers associated around the metal ion through coordination by His102 residues from each subunit of the tetramer. Comparison of independent subunits from different crystal forms indicates changes in the relative arrangement of the N-and C-terminal domains in response to metal binding. The improved ability of engineered versions of UreE containing hexahistidine sequences at either the N-terminal or C-terminal end to provide Ni 2þ for the final metal sink (urease) is eliminated in the H102A version. Therefore, the ability of the improved Ni 2þ -binding versions to deliver more nickel is likely an effect of an increased local concentration of metal ions that can rapidly replenish transferred ions bound to His102.

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

“…4E). Previous studies have shown that Hp UreE is usually found as a dimer in solution [8, 9]; in addition crystal structures of metal-bound forms of HpUreE revealed that dimers of UreE dimers (“kissing” dimers) can associate around the metal ion (Cu 2+ , Ni 2+ or Zn 2+ ) through coordination by His102 residue [10]. Similar tetrameric forms have been reported in the case of Zn 2+ - bound UreE from Bacillus pasteurii [33,34] or Cu 2+ , Ni 2+ , or Zn 2+ - bound UreE from K. aerogenes [35].…”

Effects of Metal on the Biochemical Properties of Helicobacter pylori HypB, a Maturation Factor of [NiFe]-Hydrogenase and Urease

“…These additional proteins have regions rich in various combinations of metal-binding amino acids and can bind multiple nickel ions, which may compensate for the lack of a His-rich region in either HpHypB or the H. pylori UreE protein (30). Furthermore, the reduced nickel-binding capacity of H. pylori UreE has been suggested to be a plausible reason for the supplemental involvement of HpHypB in urease bioassembly (60). In support of this hypothesis, H. pylori UreE with a synthetically attached His-rich sequence can rescue the urease activity in H. pylori hypA and hypB deletion mutants (3).…”

Biosynthesis of the Urease Metallocenter

“…The full-length zinc-bound S. pasteurii UreE dimeric structure (code 1EAR) exhibits close similarity to the K. aerogenes protein, lacks the C-terminal His-rich region and the two peripheral sites, and binds a single Zn 2ϩ ion (presumably substituting for Ni 2ϩ ) at the interfacial site (63). Structures of several forms of H. pylori UreE are known, including the nickel-bound species (codes 3L9Z and 3TJ8) (64,65), in which the Ni 2ϩ is coordinated at the interfacial site with an additional His residue provided from the C terminus. These highly soluble proteins are proposed to bind metal ions in the cytoplasm and specifically deliver nickel to urease within the complex of other accessory proteins.…”