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1n9b

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[[Image:1n9b.png|left|200px]]
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{{STRUCTURE_1n9b| PDB=1n9b | SCENE= }}
{{STRUCTURE_1n9b| PDB=1n9b | SCENE= }}
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'''Ultrahigh resolution structure of a class A beta-lactamase: On the mechanism and specificity of the extended-spectrum SHV-2 enzyme'''
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===Ultrahigh resolution structure of a class A beta-lactamase: On the mechanism and specificity of the extended-spectrum SHV-2 enzyme===
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==Overview==
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Bacterial beta-lactamases hydrolyze beta-lactam antibiotics such as penicillins and cephalosporins. The TEM-type class A beta-lactamase SHV-2 is a natural variant that exhibits activity against third-generation cephalosporins normally resistant to hydrolysis by class A enzymes. SHV-2 contains a single Gly238Ser change relative to the wild-type enzyme SHV-1. Crystallographic refinement of a model including hydrogen atoms gave R and R(free) of 12.4% and 15.0% for data to 0.91 A resolution. The hydrogen atom on the O(gamma) atom of the reactive Ser70 is clearly seen for the first time, bridging to the water molecule activated by Glu166. Though hydrogen atoms on the nearby Lys73 are not seen, this observation of the Ser70 hydrogen atom and the hydrogen bonding pattern around Lys73 indicate that Lys73 is protonated. These findings support a role for the Glu166-water couple, rather than Lys73, as the general base in the deprotonation of Ser70 in the acylation process of class A beta-lactamases. Overlay of SHV-2 with SHV-1 shows a significant 1-3 A displacement in the 238-242 beta-strand-turn segment, making the beta-lactam binding site more open to newer cephalosporins with large C7 substituents and thereby expanding the substrate spectrum of the variant enzyme. The OH group of the buried Ser238 side-chain hydrogen bonds to the main-chain CO of Asn170 on the Omega loop, that is unaltered in position relative to SHV-1. This structural role for Ser238 in protein-protein binding makes less likely its hydrogen bonding to oximino cephalosporins such as cefotaxime or ceftazidime.
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(as it appears on PubMed at http://www.pubmed.gov), where 12684014 is the PubMed ID number.
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{{ABSTRACT_PUBMED_12684014}}
==About this Structure==
==About this Structure==
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[[Category: Radiation damage]]
[[Category: Radiation damage]]
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Wed Jun 25 04:51:08 2008''
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''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Mon Jul 28 10:15:31 2008''

Revision as of 07:15, 28 July 2008

Image:1n9b.png

Template:STRUCTURE 1n9b

Ultrahigh resolution structure of a class A beta-lactamase: On the mechanism and specificity of the extended-spectrum SHV-2 enzyme

Template:ABSTRACT PUBMED 12684014

About this Structure

1N9B is a Single protein structure of sequence from Klebsiella pneumoniae. Full crystallographic information is available from OCA.

Reference

Ultrahigh resolution structure of a class A beta-lactamase: on the mechanism and specificity of the extended-spectrum SHV-2 enzyme., Nukaga M, Mayama K, Hujer AM, Bonomo RA, Knox JR, J Mol Biol. 2003 Apr 18;328(1):289-301. PMID:12684014

Page seeded by OCA on Mon Jul 28 10:15:31 2008

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