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1ck3

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{{STRUCTURE_1ck3| PDB=1ck3 | SCENE= }}
{{STRUCTURE_1ck3| PDB=1ck3 | SCENE= }}
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'''N276D MUTANT OF ESCHERICHIA COLI TEM-1 BETA-LACTAMASE'''
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===N276D MUTANT OF ESCHERICHIA COLI TEM-1 BETA-LACTAMASE===
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==Overview==
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The clinical use of beta-lactam antibiotics combined with beta-lactamase inactivators, such as clavulanate, has resulted in selection of beta-lactamases that are insensitive to inactivation by these molecules. Therefore, therapeutic combinations of an enzyme inactivator and a penicillin are harmless for bacteria harboring such an enzyme. The TEM beta-lactamase variants are the most frequently encountered enzymes of this type, and presently, 20 variants are designated as inhibitor-resistant TEM ("IRT") enzymes. Three mutations appear to account for the phenotype of the majority of IRT enzymes, one of them being the Asn276Asp substitution. In this study, we have characterized the kinetic properties of the inhibition process of the wild-type TEM-1 beta-lactamase and of its Asn276Asp variant with the three clinically used inactivators, clavulanic acid (clavulanate), sulbactam, and tazobactam, and we report the X-ray structure for the mutant variant at 2.3 A resolution. The changes in kinetic parameters for the interactions of the inhibitors with the wild-type and the mutant enzymes were more pronounced for clavulanate, and relatively inconsequential for sulbactam and tazobactam. The structure of the Asn276Asp mutant enzyme revealed a significant movement of Asp276 and the formation of a salt bridge of its side chain with the guanidinium group of Arg244, the counterion of the inhibitor carboxylate. A water molecule critical for the inactivation chemistry by clavulanate, which is observed in the wild-type enzyme structure, is not present in the crystal structure of the mutant variant. Such structural changes favor the turnover process over the inactivation chemistry for clavulanate, with profound phenotypic consequences. The report herein represents the best studied example of inhibitor-resistant beta-lactamases.
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==About this Structure==
==About this Structure==
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[[Category: Clavulanate-resistant]]
[[Category: Clavulanate-resistant]]
[[Category: Hydrolase]]
[[Category: Hydrolase]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 12:49:09 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jun 30 20:51:23 2008''

Revision as of 17:51, 30 June 2008

Image:1ck3.png

Template:STRUCTURE 1ck3

N276D MUTANT OF ESCHERICHIA COLI TEM-1 BETA-LACTAMASE

Template:ABSTRACT PUBMED 10423234

About this Structure

1CK3 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.

Reference

X-ray structure of the Asn276Asp variant of the Escherichia coli TEM-1 beta-lactamase: direct observation of electrostatic modulation in resistance to inactivation by clavulanic acid., Swaren P, Golemi D, Cabantous S, Bulychev A, Maveyraud L, Mobashery S, Samama JP, Biochemistry. 1999 Jul 27;38(30):9570-6. PMID:10423234

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