1gsq
From Proteopedia
(New page: 200px<br /><applet load="1gsq" size="450" color="white" frame="true" align="right" spinBox="true" caption="1gsq, resolution 2.4Å" /> '''THREE-DIMENSIONAL STR...) |
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| - | [[Image:1gsq.gif|left|200px]]<br /><applet load="1gsq" size=" | + | [[Image:1gsq.gif|left|200px]]<br /><applet load="1gsq" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1gsq, resolution 2.4Å" /> | caption="1gsq, resolution 2.4Å" /> | ||
'''THREE-DIMENSIONAL STRUCTURE, CATALYTIC PROPERTIES AND EVOLUTION OF A SIGMA CLASS GLUTATHIONE TRANSFERASE FROM SQUID, A PROGENITOR OF THE LENS-CRYSTALLINS OF CEPHALOPODS'''<br /> | '''THREE-DIMENSIONAL STRUCTURE, CATALYTIC PROPERTIES AND EVOLUTION OF A SIGMA CLASS GLUTATHIONE TRANSFERASE FROM SQUID, A PROGENITOR OF THE LENS-CRYSTALLINS OF CEPHALOPODS'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The glutathione transferase from squid digestive gland is unique in its | + | The glutathione transferase from squid digestive gland is unique in its very high catalytic activity toward 1-chloro-2,4-dinitrobenzene and in its ancestral relationship to the genes encoding the S-crystallins of the lens of cephalopod eye. The three-dimensional structure of this glutathione transferase in complex with the product 1-(S-glutathionyl)-2,4-dinitrobenzene (GSDNB) has been solved by multiple isomorphous replacement techniques at a resolution of 2.4 A. Like the cytosolic enzymes from vertebrates, the squid protein is a dimer. The structure is similar in overall topology to the vertebrate enzymes but has a dimer interface that is unique when compared to all of the vertebrate and invertebrate structures thus far reported. The active site of the enzyme is very open, a fact that appears to correlate with the high turnover number (800 s-1 at pH 6.5) toward 1-chloro-2,4-dinitrobenzene. Both kcat and kcat/KmCDNB exhibit pH dependencies consistent with a pKa for the thiol of enzyme-bound GSH of 6.3. The enzyme is not very efficient at catalyzing the addition of GSH to enones and epoxides. This particular characteristic appears to be due to the lack of an electrophilic residue at position 106, which is often found in other GSH transferases. The F106Y mutant enzyme is much improved in catalyzing these reactions. Comparisons of the primary structure, gene structure, and three-dimensional structure with class alpha, mu, and pi enzymes support placing the squid protein in a separate enzyme class, sigma. The unique dimer interface suggests that the class sigma enzyme diverged from the ancestral precursor prior to the divergence of the precursor gene for the alpha, mu, and pi classes. |
==About this Structure== | ==About this Structure== | ||
| - | 1GSQ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ommastrephes_sloani_pacificus Ommastrephes sloani pacificus] with GDN as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Glutathione_transferase Glutathione transferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.5.1.18 2.5.1.18] Full crystallographic information is available from [http:// | + | 1GSQ is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Ommastrephes_sloani_pacificus Ommastrephes sloani pacificus] with <scene name='pdbligand=GDN:'>GDN</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Glutathione_transferase Glutathione transferase], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=2.5.1.18 2.5.1.18] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1GSQ OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Ommastrephes sloani pacificus]] | [[Category: Ommastrephes sloani pacificus]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Armstrong, R | + | [[Category: Armstrong, R N.]] |
| - | [[Category: Gilliland, G | + | [[Category: Gilliland, G L.]] |
[[Category: Ji, X.]] | [[Category: Ji, X.]] | ||
| - | [[Category: Rosenvinge, E | + | [[Category: Rosenvinge, E C.V.]] |
[[Category: GDN]] | [[Category: GDN]] | ||
[[Category: glutathione transferase]] | [[Category: glutathione transferase]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:53:35 2008'' |
Revision as of 10:53, 21 February 2008
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THREE-DIMENSIONAL STRUCTURE, CATALYTIC PROPERTIES AND EVOLUTION OF A SIGMA CLASS GLUTATHIONE TRANSFERASE FROM SQUID, A PROGENITOR OF THE LENS-CRYSTALLINS OF CEPHALOPODS
Overview
The glutathione transferase from squid digestive gland is unique in its very high catalytic activity toward 1-chloro-2,4-dinitrobenzene and in its ancestral relationship to the genes encoding the S-crystallins of the lens of cephalopod eye. The three-dimensional structure of this glutathione transferase in complex with the product 1-(S-glutathionyl)-2,4-dinitrobenzene (GSDNB) has been solved by multiple isomorphous replacement techniques at a resolution of 2.4 A. Like the cytosolic enzymes from vertebrates, the squid protein is a dimer. The structure is similar in overall topology to the vertebrate enzymes but has a dimer interface that is unique when compared to all of the vertebrate and invertebrate structures thus far reported. The active site of the enzyme is very open, a fact that appears to correlate with the high turnover number (800 s-1 at pH 6.5) toward 1-chloro-2,4-dinitrobenzene. Both kcat and kcat/KmCDNB exhibit pH dependencies consistent with a pKa for the thiol of enzyme-bound GSH of 6.3. The enzyme is not very efficient at catalyzing the addition of GSH to enones and epoxides. This particular characteristic appears to be due to the lack of an electrophilic residue at position 106, which is often found in other GSH transferases. The F106Y mutant enzyme is much improved in catalyzing these reactions. Comparisons of the primary structure, gene structure, and three-dimensional structure with class alpha, mu, and pi enzymes support placing the squid protein in a separate enzyme class, sigma. The unique dimer interface suggests that the class sigma enzyme diverged from the ancestral precursor prior to the divergence of the precursor gene for the alpha, mu, and pi classes.
About this Structure
1GSQ is a Single protein structure of sequence from Ommastrephes sloani pacificus with as ligand. Active as Glutathione transferase, with EC number 2.5.1.18 Full crystallographic information is available from OCA.
Reference
Three-dimensional structure, catalytic properties, and evolution of a sigma class glutathione transferase from squid, a progenitor of the lens S-crystallins of cephalopods., Ji X, von Rosenvinge EC, Johnson WW, Tomarev SI, Piatigorsky J, Armstrong RN, Gilliland GL, Biochemistry. 1995 Apr 25;34(16):5317-28. PMID:7727393
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