1a4b: Difference between revisions
New page: left|200px<br /><applet load="1a4b" size="450" color="white" frame="true" align="right" spinBox="true" caption="1a4b, resolution 1.91Å" /> '''AZURIN MUTANT WITH M... |
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[[Image:1a4b.gif|left|200px]]<br /><applet load="1a4b" size=" | [[Image:1a4b.gif|left|200px]]<br /><applet load="1a4b" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1a4b, resolution 1.91Å" /> | caption="1a4b, resolution 1.91Å" /> | ||
'''AZURIN MUTANT WITH MET 121 REPLACED BY HIS, PH 6.5 CRYSTAL FORM, DATA COLLECTED AT-180 DEGREES CELSIUS'''<br /> | '''AZURIN MUTANT WITH MET 121 REPLACED BY HIS, PH 6.5 CRYSTAL FORM, DATA COLLECTED AT-180 DEGREES CELSIUS'''<br /> | ||
==Overview== | ==Overview== | ||
The rack-induced bonding mechanism of metals to proteins is a useful | The rack-induced bonding mechanism of metals to proteins is a useful concept for explaining the generation of metal sites in electron transfer proteins, such as the blue copper proteins, that are designed for rapid electron transfer. The trigonal pyramidal structure imposed by the protein with three strong equatorial ligands (one Cys and two His) provides a favorable geometry for both cuprous and cupric oxidation states. However, the crystal structures of the Met121His mutant of azurin from Alcaligenes denitrificans at pH 6.5 (1.89- and 1.91-A resolutions) and pH 3.5 (2.45-A resolution) show that the preformed metal binding cavity in the protein is more flexible than expected. At high pH (6.5), the Cu site retains the same three equatorial ligands as in the wild-type azurin and adds His121 as a fourth strong ligand, creating a tetrahedral copper site geometry with a green color referred to as 1.5 type. In the low pH (3.5) structure, the protonation of His121 causes a conformational change in residues 117-123, moving His121 away from the copper. The empty coordination site is occupied by an oxygen atom of a nitrate molecule of the buffer solution. This axial ligand is coordinated less strongly, generating a distorted tetrahedral copper geometry with a blue color and spectroscopic properties of a type-1 site. These crystal structures demonstrate that blue copper proteins are flexible enough to permit a range of movement of the Cu atom along the axial direction of the trigonal pyramid. | ||
==About this Structure== | ==About this Structure== | ||
1A4B is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Achromobacter_denitrificans Achromobacter denitrificans] with CU and SO4 as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http:// | 1A4B is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Achromobacter_denitrificans Achromobacter denitrificans] with <scene name='pdbligand=CU:'>CU</scene> and <scene name='pdbligand=SO4:'>SO4</scene> as [http://en.wikipedia.org/wiki/ligands ligands]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1A4B OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: electron transport]] | [[Category: electron transport]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:40:44 2008'' | ||
Revision as of 12:40, 21 February 2008
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AZURIN MUTANT WITH MET 121 REPLACED BY HIS, PH 6.5 CRYSTAL FORM, DATA COLLECTED AT-180 DEGREES CELSIUS
OverviewOverview
The rack-induced bonding mechanism of metals to proteins is a useful concept for explaining the generation of metal sites in electron transfer proteins, such as the blue copper proteins, that are designed for rapid electron transfer. The trigonal pyramidal structure imposed by the protein with three strong equatorial ligands (one Cys and two His) provides a favorable geometry for both cuprous and cupric oxidation states. However, the crystal structures of the Met121His mutant of azurin from Alcaligenes denitrificans at pH 6.5 (1.89- and 1.91-A resolutions) and pH 3.5 (2.45-A resolution) show that the preformed metal binding cavity in the protein is more flexible than expected. At high pH (6.5), the Cu site retains the same three equatorial ligands as in the wild-type azurin and adds His121 as a fourth strong ligand, creating a tetrahedral copper site geometry with a green color referred to as 1.5 type. In the low pH (3.5) structure, the protonation of His121 causes a conformational change in residues 117-123, moving His121 away from the copper. The empty coordination site is occupied by an oxygen atom of a nitrate molecule of the buffer solution. This axial ligand is coordinated less strongly, generating a distorted tetrahedral copper geometry with a blue color and spectroscopic properties of a type-1 site. These crystal structures demonstrate that blue copper proteins are flexible enough to permit a range of movement of the Cu atom along the axial direction of the trigonal pyramid.
About this StructureAbout this Structure
1A4B is a Single protein structure of sequence from Achromobacter denitrificans with and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
Rack-induced metal binding vs. flexibility: Met121His azurin crystal structures at different pH., Messerschmidt A, Prade L, Kroes SJ, Sanders-Loehr J, Huber R, Canters GW, Proc Natl Acad Sci U S A. 1998 Mar 31;95(7):3443-8. PMID:9520385
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