title: The crystal structure of urease from Klebsiella aerogenes.
abstract: The crystal structure of urease from Klebsiella aerogenes has been determined at 2.2 A resolution and refined to an R factor of 18.2 percent. The enzyme contains four structural domains: three with novel folds playing structural roles, and an (alpha beta)8 barrel domain, which contains the bi-nickel center. The two active site nickels are 3.5 A apart. One nickel ion is coordinated by three ligands (with low occupancy of a fourth ligand) and the second is coordinated by five ligands. A carbamylated lysine provides an oxygen ligand to each nickel, explaining why carbon dioxide is required for the activation of urease apoenzyme. The structure is compatible with a catalytic mechanism whereby urea ligates Ni-1 to complete its tetrahedral coordination and a hydroxide ligand of Ni-2 attacks the carbonyl carbon. A surprisingly high structural similarity between the urease catalytic domain and that of the zinc-dependent adenosine deaminase reveals a remarkable example of active site divergence.
authors.affiliation: Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, NY 14853, USA.
authors.forename: E
authors.initials: E
authors.lastname: Jabri
authors.forename: M B
authors.initials: MB
authors.lastname: Carr
authors.forename: R P
authors.initials: RP
authors.lastname: Hausinger
authors.forename: P A
authors.initials: PA
authors.lastname: Karplus
mesh_terms: D001665:Binding Sites; D001704:Biopolymers; D002384:Catalysis; D018360:Crystallography, X-Ray; D007711:Klebsiella pneumoniae / Q000201:enzymology*; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009532:Nickel / Q000032:analysis; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014510:Urease / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001704:Biopolymers; D009532:Nickel; D014510:Urease