1yma
From Proteopedia
(New page: 200px<br /><applet load="1yma" size="450" color="white" frame="true" align="right" spinBox="true" caption="1yma, resolution 2.0Å" /> '''STRUCTURAL CHARACTERI...) |
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| - | [[Image:1yma.jpg|left|200px]]<br /><applet load="1yma" size=" | + | [[Image:1yma.jpg|left|200px]]<br /><applet load="1yma" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1yma, resolution 2.0Å" /> | caption="1yma, resolution 2.0Å" /> | ||
'''STRUCTURAL CHARACTERIZATION OF HEME LIGATION IN THE HIS64-->TYR VARIANT OF MYOGLOBIN'''<br /> | '''STRUCTURAL CHARACTERIZATION OF HEME LIGATION IN THE HIS64-->TYR VARIANT OF MYOGLOBIN'''<br /> | ||
==Overview== | ==Overview== | ||
| - | A site-specific mutant of horse heart myoglobin has been prepared in which | + | A site-specific mutant of horse heart myoglobin has been prepared in which the distal heme pocket residue, His64, is replaced by tyrosine. The structure of this myoglobin variant has been determined to 2.0-A resolution using x-ray diffraction techniques and refined to a final crystallographic R-factor of 16.9%. The polypeptide backbone conformation of the His64-->Tyr variant of myoglobin is very similar to that of the wild-type protein. However, in the variant the water normally found coordinated to the heme iron atom and hydrogen-bonded to His64 has been displaced by the hydroxyl oxygen of the Tyr64 side chain. The tyrosine oxygen atom is directly coordinated to the heme iron atom with a bond length of 2.18 A. Distortion of heme planarity and changes in the packing of the Leu29 and Leu104 side chains are related to this mutation. The ligand environment of the ferric iron has been studied by electron paramagnetic resonance (EPR) spectroscopy using crystalline material and protein in solution. The protein in solution exhibits a rhombically split ferric high spin EPR spectrum with g values of 6.64, 5.34, and 1.98. The EPR spectrum of the crystalline sample consists of two different ferric high spin signals. The main signal is similar to the signal observed in solution and is assigned to His93-Fe(III)-Tyr64 coordination. The relatively high rhombicity of this signal can be explained as arising from distortions of the heme plane seen in the crystal structure. The second, more axial high spin signal found in the crystalline state can be tentatively assigned to another form of iron ligation with a different iron-tyrosine bond length and a less distorted heme plane. |
==About this Structure== | ==About this Structure== | ||
| - | 1YMA 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:// | + | 1YMA 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=1YMA 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: Maurus, R.]] | [[Category: Maurus, R.]] | ||
[[Category: HEM]] | [[Category: HEM]] | ||
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[[Category: oxygen transport]] | [[Category: oxygen transport]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 16:06:47 2008'' |
Revision as of 14:06, 21 February 2008
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STRUCTURAL CHARACTERIZATION OF HEME LIGATION IN THE HIS64-->TYR VARIANT OF MYOGLOBIN
Overview
A site-specific mutant of horse heart myoglobin has been prepared in which the distal heme pocket residue, His64, is replaced by tyrosine. The structure of this myoglobin variant has been determined to 2.0-A resolution using x-ray diffraction techniques and refined to a final crystallographic R-factor of 16.9%. The polypeptide backbone conformation of the His64-->Tyr variant of myoglobin is very similar to that of the wild-type protein. However, in the variant the water normally found coordinated to the heme iron atom and hydrogen-bonded to His64 has been displaced by the hydroxyl oxygen of the Tyr64 side chain. The tyrosine oxygen atom is directly coordinated to the heme iron atom with a bond length of 2.18 A. Distortion of heme planarity and changes in the packing of the Leu29 and Leu104 side chains are related to this mutation. The ligand environment of the ferric iron has been studied by electron paramagnetic resonance (EPR) spectroscopy using crystalline material and protein in solution. The protein in solution exhibits a rhombically split ferric high spin EPR spectrum with g values of 6.64, 5.34, and 1.98. The EPR spectrum of the crystalline sample consists of two different ferric high spin signals. The main signal is similar to the signal observed in solution and is assigned to His93-Fe(III)-Tyr64 coordination. The relatively high rhombicity of this signal can be explained as arising from distortions of the heme plane seen in the crystal structure. The second, more axial high spin signal found in the crystalline state can be tentatively assigned to another form of iron ligation with a different iron-tyrosine bond length and a less distorted heme plane.
About this Structure
1YMA is a Single protein structure of sequence from Equus caballus with and as ligands. Full crystallographic information is available from OCA.
Reference
Structural characterization of heme ligation in the His64-->Tyr variant of myoglobin., Maurus R, Bogumil R, Luo Y, Tang HL, Smith M, Mauk AG, Brayer GD, J Biol Chem. 1994 Apr 29;269(17):12606-10. PMID:8175669
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