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| - | [[Image:1g6a.gif|left|200px]] | + | {{Seed}} |
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| | {{STRUCTURE_1g6a| PDB=1g6a | SCENE= }} | | {{STRUCTURE_1g6a| PDB=1g6a | SCENE= }} |
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| - | '''PSE-4 CARBENICILLINASE, R234K MUTANT'''
| + | ===PSE-4 CARBENICILLINASE, R234K MUTANT=== |
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| - | ==Overview==
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| - | PSE-4 is a class A beta-lactamase produced by strains of Pseudomonas aeruginosa and is highly active for the penicillin derivative carbenicillin. The crystal structure of the wild-type PSE-4 carbenicillinase has been determined to 1.95 A resolution by molecular replacement and represents the first structure of a carbenicillinase published to date. A superposition of the PSE-4 structure with that of TEM-1 shows a rms deviation of 1.3 A for 263 Calpha atoms. Most carbenicillinases are unique among class A beta-lactamases in that residue 234 is an arginine (ABL standard numbering scheme), while in all other class A enzymes this residue is a lysine. Kinetic characterization of a R234K PSE-4 mutant reveals a 50-fold reduction in k(cat)/K(m) and confirms the importance of Arg 234 for carbenicillinase activity. A comparison of the structure of the R234K mutant refined to 1.75 A resolution with the wild-type structure shows that Arg 234 stabilizes an alternate conformation of the Ser 130 side chain, not seen in other class A beta-lactamase structures. Our molecular modeling studies suggest that the position of a bound carbenicillin would be shifted relative to that of a bound benzylpenicillin in order to avoid a steric clash between the carbenicillin alpha-carboxylate group and the conserved side chain of Asn 170. The alternate conformation of the catalytic Ser 130 in wild-type PSE-4 may be involved in accommodating this shift in the bound substrate position.
| + | The line below this paragraph, {{ABSTRACT_PUBMED_11148033}}, adds the Publication Abstract to the page |
| | + | (as it appears on PubMed at http://www.pubmed.gov), where 11148033 is the PubMed ID number. |
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| | + | {{ABSTRACT_PUBMED_11148033}} |
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| | ==About this Structure== | | ==About this Structure== |
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| | [[Category: Class a beta-lactamase]] | | [[Category: Class a beta-lactamase]] |
| | [[Category: R234k mutant]] | | [[Category: R234k mutant]] |
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Fri May 2 17:11:38 2008'' | + | |
| | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 1 04:41:29 2008'' |
Revision as of 01:41, 1 July 2008
Template:STRUCTURE 1g6a
PSE-4 CARBENICILLINASE, R234K MUTANT
Template:ABSTRACT PUBMED 11148033
About this Structure
1G6A is a Single protein structure of sequence from Pseudomonas aeruginosa. Full crystallographic information is available from OCA.
Reference
Insights into the molecular basis for the carbenicillinase activity of PSE-4 beta-lactamase from crystallographic and kinetic studies., Lim D, Sanschagrin F, Passmore L, De Castro L, Levesque RC, Strynadka NC, Biochemistry. 2001 Jan 16;40(2):395-402. PMID:11148033
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