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| {{STRUCTURE_1uci| PDB=1uci | SCENE= }} | | {{STRUCTURE_1uci| PDB=1uci | SCENE= }} |
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| '''Mutants of RNase Sa'''
| | ===Mutants of RNase Sa=== |
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| ==Overview==
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| We previously suggested that proteins gain more stability from the burial and hydrogen bonding of polar groups than from the burial of nonpolar groups (Pace, C. N. (2001) Biochemistry 40, 310-313). To study this further, we prepared eight Thr-to-Val mutants of RNase Sa, four in which the Thr side chain is hydrogen-bonded and four in which it is not. We measured the stability of these mutants by analyzing their thermal denaturation curves. The four hydrogen-bonded Thr side chains contribute 1.3 +/- 0.9 kcal/mol to the stability; those that are not still contribute 0.4 +/- 0.9 kcal/mol to the stability. For 40 Thr-to-Val mutants of 11 proteins, the average decrease in stability is 1.0 +/- 1.0 kcal/mol when the Thr side chain is hydrogen-bonded and 0.0 +/- 0.5 kcal/mol when it is not. This is clear evidence that hydrogen bonds contribute favorably to protein stability. In addition, we prepared four Val-to-Thr mutants of RNase Sa, measured their stability, and determined their crystal structures. In all cases, the mutants are less stable than the wild-type protein, with the decreases in stability ranging from 0.5 to 4.4 kcal/mol. For 41 Val-to-Thr mutants of 11 proteins, the average decrease in stability is 1.8 +/- 1.3 kcal/mol and is unfavorable for 40 of 41 mutants. This shows that placing an [bond]OH group at a site designed for a [bond]CH3 group is very unfavorable. So, [bond]OH groups can contribute favorably to protein stability, even if they are not hydrogen-bonded, if the site was selected for an [bond]OH group, but they will make an unfavorable contribution to stability, even if they are hydrogen-bonded, when they are placed at a site selected for a [bond]CH3 group. The contribution that polar groups make to protein stability depends strongly on their environment.
| | The line below this paragraph, {{ABSTRACT_PUBMED_12799387}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 12799387 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_12799387}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Hydrogen bond]] | | [[Category: Hydrogen bond]] |
| [[Category: Protein stability]] | | [[Category: Protein stability]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sat May 3 11:02:29 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 12:41:31 2008'' |