1hrm
From Proteopedia
(New page: 200px<br /><applet load="1hrm" size="450" color="white" frame="true" align="right" spinBox="true" caption="1hrm, resolution 1.7Å" /> '''THE PROXIMAL LIGAND V...) |
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| - | [[Image:1hrm.jpg|left|200px]]<br /><applet load="1hrm" size=" | + | [[Image:1hrm.jpg|left|200px]]<br /><applet load="1hrm" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1hrm, resolution 1.7Å" /> | caption="1hrm, resolution 1.7Å" /> | ||
'''THE PROXIMAL LIGAND VARIANT HIS93TYR OF HORSE HEART MYOGLOBIN'''<br /> | '''THE PROXIMAL LIGAND VARIANT HIS93TYR OF HORSE HEART MYOGLOBIN'''<br /> | ||
==Overview== | ==Overview== | ||
| - | The spectroscopic and structural properties of the His93Tyr variant of | + | The spectroscopic and structural properties of the His93Tyr variant of horse heart myoglobin have been studied to assess the effects of replacing the proximal His residue of this protein with a tyrosyl residue as occurs in catalases from various sources. The variant in the ferric form exhibits electronic spectra that are independent of pH between pH 7 and 10, and it exhibits changes in absorption maxima and intensity that are consistent with a five-coordinate heme iron center at the active site. The EPR spectrum of the variant is that of a high-spin, rhombic system similar to that reported for bovine liver catalase. The 1D 1H-NMR spectrum of the variant confirms the five-coordinate nature of the heme iron center and exhibits a broad resonance at 112.5 ppm that is attributable to the meta protons of the phenolate ligand. This result indicates that the new Tyr ligand flips at a significant rate in this protein. The thermal stability of the Fe(III) derivative is unchanged from that of the wild-type protein (pH 8) while the midpoint reduction potential [-208 mV vs SHE (pH 8.0, 25 degrees C)] is about 250 mV lower. The three-dimensional structure of the variant determined by X-ray diffraction analysis confirms the five-coordinate nature of the heme iron center and establishes that the introduction of a proximal Tyr ligand is accommodated by a shift of the F helix (residues 88-99) in which this residue resides away from the heme pocket. Additional effects of this change are small shifts in the positions of Leu29, a heme propionate, and a heme vinyl group that are accompanied by altered hydrogen bonding interactions with the heme prosthetic group.(ABSTRACT TRUNCATED AT 250 WORDS) |
==About this Structure== | ==About this Structure== | ||
| - | 1HRM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Equus_caballus Equus caballus] with SO4 and HEM as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | + | 1HRM is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Equus_caballus Equus caballus] with <scene name='pdbligand=SO4:'>SO4</scene> and <scene name='pdbligand=HEM:'>HEM</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1HRM OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Equus caballus]] | [[Category: Equus caballus]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Brayer, G | + | [[Category: Brayer, G D.]] |
| - | [[Category: Burk, D | + | [[Category: Burk, D L.]] |
[[Category: HEM]] | [[Category: HEM]] | ||
[[Category: SO4]] | [[Category: SO4]] | ||
[[Category: oxygen transport]] | [[Category: oxygen transport]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 13:04:11 2008'' |
Revision as of 11:04, 21 February 2008
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THE PROXIMAL LIGAND VARIANT HIS93TYR OF HORSE HEART MYOGLOBIN
Overview
The spectroscopic and structural properties of the His93Tyr variant of horse heart myoglobin have been studied to assess the effects of replacing the proximal His residue of this protein with a tyrosyl residue as occurs in catalases from various sources. The variant in the ferric form exhibits electronic spectra that are independent of pH between pH 7 and 10, and it exhibits changes in absorption maxima and intensity that are consistent with a five-coordinate heme iron center at the active site. The EPR spectrum of the variant is that of a high-spin, rhombic system similar to that reported for bovine liver catalase. The 1D 1H-NMR spectrum of the variant confirms the five-coordinate nature of the heme iron center and exhibits a broad resonance at 112.5 ppm that is attributable to the meta protons of the phenolate ligand. This result indicates that the new Tyr ligand flips at a significant rate in this protein. The thermal stability of the Fe(III) derivative is unchanged from that of the wild-type protein (pH 8) while the midpoint reduction potential [-208 mV vs SHE (pH 8.0, 25 degrees C)] is about 250 mV lower. The three-dimensional structure of the variant determined by X-ray diffraction analysis confirms the five-coordinate nature of the heme iron center and establishes that the introduction of a proximal Tyr ligand is accommodated by a shift of the F helix (residues 88-99) in which this residue resides away from the heme pocket. Additional effects of this change are small shifts in the positions of Leu29, a heme propionate, and a heme vinyl group that are accompanied by altered hydrogen bonding interactions with the heme prosthetic group.(ABSTRACT TRUNCATED AT 250 WORDS)
About this Structure
1HRM is a Single protein structure of sequence from Equus caballus with and as ligands. Full crystallographic information is available from OCA.
Reference
The proximal ligand variant His93Tyr of horse heart myoglobin., Hildebrand DP, Burk DL, Maurus R, Ferrer JC, Brayer GD, Mauk AG, Biochemistry. 1995 Feb 14;34(6):1997-2005. PMID:7849057
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