Salt bridges: Difference between revisions
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<applet load='1cbr' size='300' frame='true' align='right' caption='Salt bridge between retinoic acid(-) and arg131(+) in [[1cbr]].' | <applet load='1cbr' size='300' frame='true' align='right' caption='Salt bridge between retinoic acid(-) and arg131(+) in [[1cbr]].' | ||
scene='Salt_bridges/Salt_bridge/ | scene='Salt_bridges/Salt_bridge/2' /> | ||
In proteins, salt bridges occur between amino acid side-chains with opposite positive or negative full-electron charges, namely, (at neutral pH) Glu- or Asp- vs. Arg+ or Lys+. They may also occur between ionized organic ligands, such as acetylcholine+ (or example at right: [[1cbr]]), or inorganic ions, such as K<sup>+</sup> or SO<sub>4</sub><sup>=</sup>, and amino acid side-chains. | In proteins, salt bridges occur between amino acid side-chains with opposite positive or negative full-electron charges, namely, (at neutral pH) Glu- or Asp- vs. Arg+ or Lys+. They may also occur between ionized organic ligands, such as acetylcholine+ (or example at right: [[1cbr]]), or inorganic ions, such as K<sup>+</sup> or SO<sub>4</sub><sup>=</sup>, and amino acid side-chains. | ||
Revision as of 02:05, 26 April 2012
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In proteins, salt bridges occur between amino acid side-chains with opposite positive or negative full-electron charges, namely, (at neutral pH) Glu- or Asp- vs. Arg+ or Lys+. They may also occur between ionized organic ligands, such as acetylcholine+ (or example at right: 1cbr), or inorganic ions, such as K+ or SO4=, and amino acid side-chains.
A salt bridge is generally considered to exist when the centers of charge are 4 Å or less apart[1]. The center of charge of the arginine sidechain is the zeta carbon[2]. The energetic significance of such complementary charge pairs is a complex function of the local environment.
Proteins from thermophiles have more salt bridges than do proteins from mesophiles[3][4]. These additional salt bridges contribute to stability, resisting denaturation by high temperature[5].
ExamplesExamples
Ultraviolet-B receptorUltraviolet-B receptor
UVR8 is an ultraviolet-B receptor in plants such as Arabidopsis. It is a homodimer that, upon irradiation, dissociates into a monomer involved in transcriptional activation of UV protective proteins[6]. Unexpectedly, high ionic strength was found to dissociate the dimer. The homodimer 4dnw contains many salt bridges and cation-pi interactions at the interface. More.
VisualizationVisualization
Putative salt bridges can be displayed by FirstGlance in Jmol.
ReferencesReferences
- ↑ Jeffrey, George A., An introduction to hydrogen bonding, Oxford University Press, 1997. Page 192.
- ↑ Gallivan JP, Dougherty DA. Cation-pi interactions in structural biology. Proc Natl Acad Sci U S A. 1999 Aug 17;96(17):9459-64. PMID:10449714
- ↑ Das R, Gerstein M. The stability of thermophilic proteins: a study based on comprehensive genome comparison. Funct Integr Genomics. 2000 May;1(1):76-88. PMID:11793224 doi:10.1007/s101420000003
- ↑ Kumar S, Nussinov R. How do thermophilic proteins deal with heat? Cell Mol Life Sci. 2001 Aug;58(9):1216-33. PMID:11577980
- ↑ Chan CH, Yu TH, Wong KB. Stabilizing salt-bridge enhances protein thermostability by reducing the heat capacity change of unfolding. PLoS One. 2011;6(6):e21624. Epub 2011 Jun 24. PMID:21720566 doi:10.1371/journal.pone.0021624
- ↑ Wu D, Hu Q, Yan Z, Chen W, Yan C, Huang X, Zhang J, Yang P, Deng H, Wang J, Deng X, Shi Y. Structural basis of ultraviolet-B perception by UVR8. Nature. 2012 Feb 29;484(7393):214-9. doi: 10.1038/nature10931. PMID:22388820 doi:10.1038/nature10931