1eq5
From Proteopedia
(New page: 200px<br /> <applet load="1eq5" size="450" color="white" frame="true" align="right" spinBox="true" caption="1eq5, resolution 1.8Å" /> '''CRYSTAL STRUCTURES O...) |
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| - | [[Image:1eq5.gif|left|200px]]<br /> | + | [[Image:1eq5.gif|left|200px]]<br /><applet load="1eq5" size="350" color="white" frame="true" align="right" spinBox="true" |
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caption="1eq5, resolution 1.8Å" /> | caption="1eq5, resolution 1.8Å" /> | ||
'''CRYSTAL STRUCTURES OF SALT BRIDGE MUTANTS OF HUMAN LYSOZYME'''<br /> | '''CRYSTAL STRUCTURES OF SALT BRIDGE MUTANTS OF HUMAN LYSOZYME'''<br /> | ||
==Overview== | ==Overview== | ||
| - | Salt bridges play important roles in the conformational stability of | + | Salt bridges play important roles in the conformational stability of proteins. However, the effect of a surface salt bridge on the stability remains controversial even today; some reports have shown little contribution of a surface salt bridge to stability, whereas others have shown a favorable contribution. In this study, to elucidate the net contribution of a surface salt bridge to the conformational stability of a protein, systematic mutant human lysozymes, containing one Glu to Gln (E7Q) and five Asp to Asn mutations (D18N, D49N, D67N, D102N, and D120N) at residues where a salt bridge is formed near the surface in the wild-type structure, were examined. The thermodynamic parameters for denaturation between pH 2.0 and 4.8 were determined by use of a differential scanning calorimeter, and the crystal structures were analyzed by X-ray crystallography. The denaturation Gibbs energy (DeltaG) of all mutant proteins was lower than that of the wild-type protein at pH 4, whereas there was little difference between them near pH 2. This is caused by the fact that the Glu and Asp residues are ionized at pH 4 but protonated at pH 2, indicating a favorable contribution of salt bridges to the wild-type structure at pH 4. Each contribution was not equivalent, but we found that the contributions correlate with the solvent inaccessibility of the salt bridges; the salt bridge contribution was small when 100% accessible, while it was about 9 kJ/mol if 100% inaccessible. This conclusion indicates how to reconcile a number of conflicting reports about role of surface salt bridges in protein stability. Furthermore, the effect of salts on surface salt bridges was also examined. In the presence of 0.2 M KCl, the stability at pH 4 decreased, and the differences in stability between the wild-type and mutant proteins were smaller than those in the absence of salts, indicating the compensation to the contribution of salt bridges with salts. Salt bridges with more than 50% accessibility did not contribute to the stability in the presence of 0.2 M KCl. |
==Disease== | ==Disease== | ||
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==About this Structure== | ==About this Structure== | ||
| - | 1EQ5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with NA as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Lysozyme Lysozyme], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.17 3.2.1.17] Full crystallographic information is available from [http:// | + | 1EQ5 is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Homo_sapiens Homo sapiens] with <scene name='pdbligand=NA:'>NA</scene> as [http://en.wikipedia.org/wiki/ligand ligand]. Active as [http://en.wikipedia.org/wiki/Lysozyme Lysozyme], with EC number [http://www.brenda-enzymes.info/php/result_flat.php4?ecno=3.2.1.17 3.2.1.17] Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1EQ5 OCA]. |
==Reference== | ==Reference== | ||
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[[Category: stability]] | [[Category: stability]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:30:28 2008'' |
Revision as of 10:30, 21 February 2008
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CRYSTAL STRUCTURES OF SALT BRIDGE MUTANTS OF HUMAN LYSOZYME
Contents |
Overview
Salt bridges play important roles in the conformational stability of proteins. However, the effect of a surface salt bridge on the stability remains controversial even today; some reports have shown little contribution of a surface salt bridge to stability, whereas others have shown a favorable contribution. In this study, to elucidate the net contribution of a surface salt bridge to the conformational stability of a protein, systematic mutant human lysozymes, containing one Glu to Gln (E7Q) and five Asp to Asn mutations (D18N, D49N, D67N, D102N, and D120N) at residues where a salt bridge is formed near the surface in the wild-type structure, were examined. The thermodynamic parameters for denaturation between pH 2.0 and 4.8 were determined by use of a differential scanning calorimeter, and the crystal structures were analyzed by X-ray crystallography. The denaturation Gibbs energy (DeltaG) of all mutant proteins was lower than that of the wild-type protein at pH 4, whereas there was little difference between them near pH 2. This is caused by the fact that the Glu and Asp residues are ionized at pH 4 but protonated at pH 2, indicating a favorable contribution of salt bridges to the wild-type structure at pH 4. Each contribution was not equivalent, but we found that the contributions correlate with the solvent inaccessibility of the salt bridges; the salt bridge contribution was small when 100% accessible, while it was about 9 kJ/mol if 100% inaccessible. This conclusion indicates how to reconcile a number of conflicting reports about role of surface salt bridges in protein stability. Furthermore, the effect of salts on surface salt bridges was also examined. In the presence of 0.2 M KCl, the stability at pH 4 decreased, and the differences in stability between the wild-type and mutant proteins were smaller than those in the absence of salts, indicating the compensation to the contribution of salt bridges with salts. Salt bridges with more than 50% accessibility did not contribute to the stability in the presence of 0.2 M KCl.
Disease
Known diseases associated with this structure: Amyloidosis, renal OMIM:[153450], Microphthalmia, syndromic 1 OMIM:[309800]
About this Structure
1EQ5 is a Single protein structure of sequence from Homo sapiens with as ligand. Active as Lysozyme, with EC number 3.2.1.17 Full crystallographic information is available from OCA.
Reference
Contribution of salt bridges near the surface of a protein to the conformational stability., Takano K, Tsuchimori K, Yamagata Y, Yutani K, Biochemistry. 2000 Oct 10;39(40):12375-81. PMID:11015217
Page seeded by OCA on Thu Feb 21 12:30:28 2008
Categories: Homo sapiens | Lysozyme | Single protein | Takano, K. | Tsuchimori, K. | Yamagata, Y. | Yutani, K. | NA | Salt bridge | Stability
