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| {{STRUCTURE_1krc| PDB=1krc | SCENE= }} | | {{STRUCTURE_1krc| PDB=1krc | SCENE= }} |
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| '''CRYSTAL STRUCTURE OF KLEBSIELLA AEROGENES UREASE, ITS APOENZYME AND TWO ACTIVE SITE MUTANTS'''
| | ===CRYSTAL STRUCTURE OF KLEBSIELLA AEROGENES UREASE, ITS APOENZYME AND TWO ACTIVE SITE MUTANTS=== |
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| ==Overview==
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| 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.
| | The line below this paragraph, {{ABSTRACT_PUBMED_8718850}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 8718850 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_8718850}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Active site mutant]] | | [[Category: Active site mutant]] |
| [[Category: Nickel metalloenzyme]] | | [[Category: Nickel metalloenzyme]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 23:04:51 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jul 2 10:49:59 2008'' |
