1d8u
From Proteopedia
(New page: 200px<br /> <applet load="1d8u" size="450" color="white" frame="true" align="right" spinBox="true" caption="1d8u, resolution 2.35Å" /> '''CRYSTAL STRUCTURE O...) |
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| - | [[Image:1d8u.gif|left|200px]]<br /> | + | [[Image:1d8u.gif|left|200px]]<br /><applet load="1d8u" size="350" color="white" frame="true" align="right" spinBox="true" |
| - | <applet load="1d8u" size=" | + | |
caption="1d8u, resolution 2.35Å" /> | caption="1d8u, resolution 2.35Å" /> | ||
'''CRYSTAL STRUCTURE OF NON-SYMBIOTIC PLANT HEMOGLOBIN FROM RICE'''<br /> | '''CRYSTAL STRUCTURE OF NON-SYMBIOTIC PLANT HEMOGLOBIN FROM RICE'''<br /> | ||
==Overview== | ==Overview== | ||
| - | BACKGROUND: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant | + | BACKGROUND: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant proteins that is distinct genetically and structurally from leghemoglobins. They are found ubiquitously in plants and are expressed in low concentrations in a variety of tissues including roots and leaves. Their function involves a biochemical response to growth under limited O(2) conditions. RESULTS: The first X-ray crystal structure of a member of this class of proteins, riceHb1, has been determined to 2.4 A resolution using a combination of phasing techniques. The active site of ferric riceHb1 differs significantly from those of traditional hemoglobins and myoglobins. The proximal and distal histidine sidechains coordinate directly to the heme iron, forming a hemichrome with spectral properties similar to those of cytochrome b(5). The crystal structure also shows that riceHb1 is a dimer with a novel interface formed by close contacts between the G helix and the region between the B and C helices of the partner subunit. CONCLUSIONS: The bis-histidyl heme coordination found in riceHb1 is unusual for a protein that binds O(2) reversibly. However, the distal His73 is rapidly displaced by ferrous ligands, and the overall O(2) affinity is ultra-high (K(D) approximately 1 nM). Our crystallographic model suggests that ligand binding occurs by an upward and outward movement of the E helix, concomitant dissociation of the distal histidine, possible repacking of the CD corner and folding of the D helix. Although the functional relevance of quaternary structure in nsHbs is unclear, the role of two conserved residues in stabilizing the dimer interface has been identified. |
==About this Structure== | ==About this Structure== | ||
| - | 1D8U is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryza_sativa Oryza sativa] with HEM as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http:// | + | 1D8U is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Oryza_sativa Oryza sativa] with <scene name='pdbligand=HEM:'>HEM</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1D8U OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Oryza sativa]] | [[Category: Oryza sativa]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Brucker, E | + | [[Category: Brucker, E A.]] |
[[Category: Hargrove, M.]] | [[Category: Hargrove, M.]] | ||
| - | [[Category: Jr., G | + | [[Category: Jr., G N.Phillips.]] |
| - | [[Category: Olson, J | + | [[Category: Olson, J S.]] |
[[Category: Stec, B.]] | [[Category: Stec, B.]] | ||
[[Category: HEM]] | [[Category: HEM]] | ||
| Line 25: | Line 24: | ||
[[Category: oxygen storage/transport]] | [[Category: oxygen storage/transport]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:14:09 2008'' |
Revision as of 10:14, 21 February 2008
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CRYSTAL STRUCTURE OF NON-SYMBIOTIC PLANT HEMOGLOBIN FROM RICE
Overview
BACKGROUND: Nonsymbiotic hemoglobins (nsHbs) form a new class of plant proteins that is distinct genetically and structurally from leghemoglobins. They are found ubiquitously in plants and are expressed in low concentrations in a variety of tissues including roots and leaves. Their function involves a biochemical response to growth under limited O(2) conditions. RESULTS: The first X-ray crystal structure of a member of this class of proteins, riceHb1, has been determined to 2.4 A resolution using a combination of phasing techniques. The active site of ferric riceHb1 differs significantly from those of traditional hemoglobins and myoglobins. The proximal and distal histidine sidechains coordinate directly to the heme iron, forming a hemichrome with spectral properties similar to those of cytochrome b(5). The crystal structure also shows that riceHb1 is a dimer with a novel interface formed by close contacts between the G helix and the region between the B and C helices of the partner subunit. CONCLUSIONS: The bis-histidyl heme coordination found in riceHb1 is unusual for a protein that binds O(2) reversibly. However, the distal His73 is rapidly displaced by ferrous ligands, and the overall O(2) affinity is ultra-high (K(D) approximately 1 nM). Our crystallographic model suggests that ligand binding occurs by an upward and outward movement of the E helix, concomitant dissociation of the distal histidine, possible repacking of the CD corner and folding of the D helix. Although the functional relevance of quaternary structure in nsHbs is unclear, the role of two conserved residues in stabilizing the dimer interface has been identified.
About this Structure
1D8U is a Single protein structure of sequence from Oryza sativa with as ligand. Full crystallographic information is available from OCA.
Reference
Crystal structure of a nonsymbiotic plant hemoglobin., Hargrove MS, Brucker EA, Stec B, Sarath G, Arredondo-Peter R, Klucas RV, Olson JS, Phillips GN Jr, Structure. 2000 Sep 15;8(9):1005-14. PMID:10986467
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