1krb
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| , resolution 2.5Å | |||||||
|---|---|---|---|---|---|---|---|
| Ligands: | and | ||||||
| Activity: | Urease, with EC number 3.5.1.5 | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
CRYSTAL STRUCTURE OF KLEBSIELLA AEROGENES UREASE, ITS APOENZYME AND TWO ACTIVE SITE MUTANTS
OverviewOverview
Urease from Klebsiella aerogenes [Jabri et al. (1995) Science 268, 998-1004] is an (alpha beta gamma)3 trimer with each alpha-subunit having an (alpha beta)8-barrel domain containing a binickel active center. Here we examine structure-function relations for urease in more detail through structural analysis of the urease apoenzyme at 2.3 A resolution and mutants of two key catalytic residues (H219A and H320A) at 2.5 A resolution. With the exception of the active site, in which a water molecule takes the place of the missing carbamate and nickel atoms, the structure of the apoenzyme is nearly identical to that of the holoenzyme, suggesting a high degree of preorganization which helps explain the tight binding of nickel. In the structure of H219A, the major change involves a conformational shift and ordering of the active site flap, but a small shift in the side chain of Asp alpha 221 could contribute to the lower activity of H219A. In the H320A structure, the catalytic water, primarily a Ni-2 ligand in the holoenzyme, shifts into a bridging position. This shift shows that the nickel ligation is rather sensitive to the environment and the change in ligation may contribute to the 10(5)-fold lower activity of H320A. In addition, these results show that urease is resilient to the loss of nickel ions and mutations. Analysis of the urease tertiary/quaternary structure suggests that the stability of this enzyme may be largely due to its burial of an unusually large fraction of its residues: 50% in the gamma-subunit, 30% in the beta-subunit, and 60% in the alpha-subunit.
About this StructureAbout this Structure
1KRB is a Protein complex structure of sequences from Klebsiella aerogenes. Full crystallographic information is available from OCA.
ReferenceReference
Structures of the Klebsiella aerogenes urease apoenzyme and two active-site mutants., Jabri E, Karplus PA, Biochemistry. 1996 Aug 20;35(33):10616-26. PMID:8718850
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