1c0n
From Proteopedia
(New page: 200px<br /><applet load="1c0n" size="450" color="white" frame="true" align="right" spinBox="true" caption="1c0n, resolution 2.8Å" /> '''CSDB PROTEIN, NIFS HO...) |
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| - | [[Image:1c0n.gif|left|200px]]<br /><applet load="1c0n" size=" | + | [[Image:1c0n.gif|left|200px]]<br /><applet load="1c0n" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1c0n, resolution 2.8Å" /> | caption="1c0n, resolution 2.8Å" /> | ||
'''CSDB PROTEIN, NIFS HOMOLOGUE'''<br /> | '''CSDB PROTEIN, NIFS HOMOLOGUE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Escherichia coli CsdB, a NifS homologue with a high specificity for | + | Escherichia coli CsdB, a NifS homologue with a high specificity for L-selenocysteine, is a pyridoxal 5'-phosphate (PLP)-dependent dimeric enzyme that belongs to aminotransferases class V in fold-type I of PLP enzymes and catalyzes the decomposition of L-selenocysteine into selenium and L-alanine. The crystal structure of the enzyme has been determined by the X-ray crystallographic method of multiple isomorphous replacement and refined to an R-factor of 18.7% at 2.8 A resolution. The subunit structure consists of three parts: a large domain of an alpha/beta-fold containing a seven-stranded beta-sheet flanked by seven helices, a small domain containing a four-stranded antiparallel beta-sheet flanked by three alpha-helices, and an N-terminal segment containing two alpha-helices. The overall fold of the subunit is similar to those of the enzymes belonging to the fold-type I family represented by aspartate aminotransferase. However, CsdB has several structural features that are not observed in other families of the enzymes. A remarkable feature is that an alpha-helix in the lobe extending from the small domain to the large domain in one subunit of the dimer interacts with a beta-hairpin loop protruding from the large domain of the other subunit. The extended lobe and the protruded beta-hairpin loop form one side of a limb of each active site in the enzyme. The most striking structural feature of CsdB lies in the location of a putative catalytic residue; the side chain of Cys364 on the extended lobe of one subunit is close enough to interact with the gamma-atom of a modeled substrate in the active site of the subunit. Moreover, His55 from the other subunit is positioned so that it interacts with the gamma- or beta-atom of the substrate and may be involved in the catalytic reaction. This is the first report on three-dimensional structures of NifS homologues. |
==About this Structure== | ==About this Structure== | ||
| - | 1C0N is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with PLP and ACY as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 1C0N is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli] with <scene name='pdbligand=PLP:'>PLP</scene> and <scene name='pdbligand=ACY:'>ACY</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1C0N OCA]. |
==Reference== | ==Reference== | ||
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[[Category: alpha/beta fold]] | [[Category: alpha/beta fold]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:01:07 2008'' |
Revision as of 10:01, 21 February 2008
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CSDB PROTEIN, NIFS HOMOLOGUE
Overview
Escherichia coli CsdB, a NifS homologue with a high specificity for L-selenocysteine, is a pyridoxal 5'-phosphate (PLP)-dependent dimeric enzyme that belongs to aminotransferases class V in fold-type I of PLP enzymes and catalyzes the decomposition of L-selenocysteine into selenium and L-alanine. The crystal structure of the enzyme has been determined by the X-ray crystallographic method of multiple isomorphous replacement and refined to an R-factor of 18.7% at 2.8 A resolution. The subunit structure consists of three parts: a large domain of an alpha/beta-fold containing a seven-stranded beta-sheet flanked by seven helices, a small domain containing a four-stranded antiparallel beta-sheet flanked by three alpha-helices, and an N-terminal segment containing two alpha-helices. The overall fold of the subunit is similar to those of the enzymes belonging to the fold-type I family represented by aspartate aminotransferase. However, CsdB has several structural features that are not observed in other families of the enzymes. A remarkable feature is that an alpha-helix in the lobe extending from the small domain to the large domain in one subunit of the dimer interacts with a beta-hairpin loop protruding from the large domain of the other subunit. The extended lobe and the protruded beta-hairpin loop form one side of a limb of each active site in the enzyme. The most striking structural feature of CsdB lies in the location of a putative catalytic residue; the side chain of Cys364 on the extended lobe of one subunit is close enough to interact with the gamma-atom of a modeled substrate in the active site of the subunit. Moreover, His55 from the other subunit is positioned so that it interacts with the gamma- or beta-atom of the substrate and may be involved in the catalytic reaction. This is the first report on three-dimensional structures of NifS homologues.
About this Structure
1C0N is a Single protein structure of sequence from Escherichia coli with and as ligands. Full crystallographic information is available from OCA.
Reference
Structure of a NifS homologue: X-ray structure analysis of CsdB, an Escherichia coli counterpart of mammalian selenocysteine lyase., Fujii T, Maeda M, Mihara H, Kurihara T, Esaki N, Hata Y, Biochemistry. 2000 Feb 15;39(6):1263-73. PMID:10684605
Page seeded by OCA on Thu Feb 21 12:01:07 2008
Categories: Escherichia coli | Single protein | Esaki, N. | Fujii, T. | Hata, Y. | Kurihara, T. | Maeda, M. | Mihara, H. | ACY | PLP | Alpha/beta fold
