1g6a: Difference between revisions

Revision as of 13:46, 21 February 2008

PSE-4 CARBENICILLINASE, R234K MUTANT

OverviewOverview

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.

About this StructureAbout this Structure

1G6A is a Single protein structure of sequence from Pseudomonas aeruginosa with as ligand. Active as Beta-lactamase, with EC number 3.5.2.6 Full crystallographic information is available from OCA.

ReferenceReference

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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-[[Image:1g6a.gif|left|200px]]<br /><applet load="1g6a" size="450" color="white" frame="true" align="right" spinBox="true"
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 caption="1g6a, resolution 1.75&Aring;" />
 '''PSE-4 CARBENICILLINASE, R234K MUTANT'''<br />
 ==Overview==
-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.
+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.
 ==About this Structure==
-G6A is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_aeruginosa Pseudomonas aeruginosa] with SO4 as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Beta-lactamase Beta-lactamase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.2.6 3.5.2.6] Full crystallographic information is available from [http://ispc.weizmann.ac.il/oca-bin/ocashort?id=1G6A OCA].
+G6A is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Pseudomonas_aeruginosa Pseudomonas aeruginosa] with <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Beta-lactamase Beta-lactamase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.5.2.6 3.5.2.6] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1G6A OCA].
 ==Reference==
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 [[Category: Pseudomonas aeruginosa]]
 [[Category: Single protein]]
-[[Category: Castro, L.De.]]
+[[Category: Castro, L De.]]
-[[Category: Levesque, R.C.]]
+[[Category: Levesque, R C.]]
 [[Category: Lim, D.]]
 [[Category: Passmore, L.]]
 [[Category: Sanschagrin, F.]]
-[[Category: Strynadka, N.C.J.]]
+[[Category: Strynadka, N C.J.]]
 [[Category: SO4]]
 [[Category: carbenicillinase]]
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 [[Category: r234k mutant]]
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