1qlm
From Proteopedia
(New page: 200px<br /><applet load="1qlm" size="450" color="white" frame="true" align="right" spinBox="true" caption="1qlm, resolution 2.00Å" /> '''THE CRYSTAL STRUCTUR...) |
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| - | [[Image:1qlm.jpg|left|200px]]<br /><applet load="1qlm" size=" | + | [[Image:1qlm.jpg|left|200px]]<br /><applet load="1qlm" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1qlm, resolution 2.00Å" /> | caption="1qlm, resolution 2.00Å" /> | ||
'''THE CRYSTAL STRUCTURE OF METHENYLTETRAHYDROMETHANOPTERIN CYCLOHYDROLASE FROM THE HYPERTHERMOPHILIC ARCHAEON METHANOPYRUS KANDLERI'''<br /> | '''THE CRYSTAL STRUCTURE OF METHENYLTETRAHYDROMETHANOPTERIN CYCLOHYDROLASE FROM THE HYPERTHERMOPHILIC ARCHAEON METHANOPYRUS KANDLERI'''<br /> | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: The reduction of carbon dioxide to methane in methanogenic | + | BACKGROUND: The reduction of carbon dioxide to methane in methanogenic archaea involves the tetrahydrofolate analogue tetrahydromethanopterin (H(4)MPT) as a C(1) unit carrier. In the third step of this reaction sequence, N(5)-formyl-H(4)MPT is converted to methenyl-H(4)MPT(+) by the enzyme methenyltetrahydromethanopterin cyclohydrolase. The cyclohydrolase from the hyperthermophilic archaeon Methanopyrus kandleri (Mch) is extremely thermostable and adapted to a high intracellular concentration of lyotropic salts. RESULTS: Mch was crystallized and its structure solved at 2.0 A resolution using a combination of the single isomorphous replacement (SIR) and multiple anomalous dispersion (MAD) techniques. The structure of the homotrimeric enzyme reveals a new alpha/beta fold that is composed of two domains forming a large sequence-conserved pocket between them. Two phosphate ions were found in and adjacent to this pocket, respectively; the latter is displaced by the phosphate moiety of the substrate formyl-H(4)MPT according to a hypothetical model of the substrate binding. CONCLUSIONS: Although the exact position of the substrate is not yet known, the residues lining the active site of Mch could be tentatively assigned. Comparison of Mch with the tetrahydrofolate-specific cyclohydrolase/dehydrogenase reveals similarities in domain arrangement and in some active-site residues, whereas the fold appears to be different. The adaptation of Mch to high salt concentrations and high temperatures is reflected by the excess of acidic residues at the trimer surface and by the higher oligomerization state of Mch compared with its mesophtic counterparts. |
==About this Structure== | ==About this Structure== | ||
| - | 1QLM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Methanopyrus_kandleri Methanopyrus kandleri] with PO4 as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | + | 1QLM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Methanopyrus_kandleri Methanopyrus kandleri] with <scene name='pdbligand=PO4:'>PO4</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1QLM OCA]. |
==Reference== | ==Reference== | ||
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[[Category: tetrahydromethanopterin]] | [[Category: tetrahydromethanopterin]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 14:41:00 2008'' |
Revision as of 12:41, 21 February 2008
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THE CRYSTAL STRUCTURE OF METHENYLTETRAHYDROMETHANOPTERIN CYCLOHYDROLASE FROM THE HYPERTHERMOPHILIC ARCHAEON METHANOPYRUS KANDLERI
Overview
BACKGROUND: The reduction of carbon dioxide to methane in methanogenic archaea involves the tetrahydrofolate analogue tetrahydromethanopterin (H(4)MPT) as a C(1) unit carrier. In the third step of this reaction sequence, N(5)-formyl-H(4)MPT is converted to methenyl-H(4)MPT(+) by the enzyme methenyltetrahydromethanopterin cyclohydrolase. The cyclohydrolase from the hyperthermophilic archaeon Methanopyrus kandleri (Mch) is extremely thermostable and adapted to a high intracellular concentration of lyotropic salts. RESULTS: Mch was crystallized and its structure solved at 2.0 A resolution using a combination of the single isomorphous replacement (SIR) and multiple anomalous dispersion (MAD) techniques. The structure of the homotrimeric enzyme reveals a new alpha/beta fold that is composed of two domains forming a large sequence-conserved pocket between them. Two phosphate ions were found in and adjacent to this pocket, respectively; the latter is displaced by the phosphate moiety of the substrate formyl-H(4)MPT according to a hypothetical model of the substrate binding. CONCLUSIONS: Although the exact position of the substrate is not yet known, the residues lining the active site of Mch could be tentatively assigned. Comparison of Mch with the tetrahydrofolate-specific cyclohydrolase/dehydrogenase reveals similarities in domain arrangement and in some active-site residues, whereas the fold appears to be different. The adaptation of Mch to high salt concentrations and high temperatures is reflected by the excess of acidic residues at the trimer surface and by the higher oligomerization state of Mch compared with its mesophtic counterparts.
About this Structure
1QLM is a Single protein structure of sequence from Methanopyrus kandleri with as ligand. Full crystallographic information is available from OCA.
Reference
The crystal structure of methenyltetrahydromethanopterin cyclohydrolase from the hyperthermophilic archaeon Methanopyrus kandleri., Grabarse W, Vaupel M, Vorholt JA, Shima S, Thauer RK, Wittershagen A, Bourenkov G, Bartunik HD, Ermler U, Structure. 1999 Oct 15;7(10):1257-68. PMID:10545331
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