Salt bridges: Difference between revisions
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In proteins, salt bridges<ref>PMID: 21287621</ref> 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<ref>PMID: 21287621</ref> 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. | ||
A salt bridge is generally considered to exist when the centers of charge are 4 Å or less apart<ref>Jeffrey, George A., An introduction to hydrogen bonding, Oxford University Press, 1997. Page 192.</ref>. The center of charge of the arginine sidechain is the zeta carbon<ref name='GD'>PMID: 10449714</ref>. The energetic significance of such complementary charge pairs is a complex function of the local environment. | A salt bridge is generally considered to exist when the centers of charge are 4 Å or less apart (<ref>Jeffrey, George A., An introduction to hydrogen bonding, Oxford University Press, 1997. Page 192.</ref> and see legend to Table 6 in ref. <ref>PMID:11080642</ref>). The center of charge of the arginine sidechain is the zeta carbon<ref name='GD'>PMID: 10449714</ref>. The energetic significance of such complementary charge pairs is a complex function of the local environment. | ||
Proteins from [[extremophiles|thermophiles]] have more salt bridges than do proteins from mesophiles<ref>PMID: 11793224</ref><ref name="kumar">PMID: 11577980</ref>. These additional salt bridges contribute to stability, resisting denaturation by high temperature<ref>PMID: 21720566</ref><ref>PMID: 31360001</ref>. | Proteins from [[extremophiles|thermophiles]] have more salt bridges than do proteins from mesophiles<ref>PMID:19164280</ref><ref>PMID: 11793224</ref><ref name="kumar">PMID: 11577980</ref>. These additional salt bridges contribute to stability, resisting denaturation by high temperature<ref>PMID: 21720566</ref><ref>PMID: 31360001</ref>. | ||
==Examples== | ==Examples== | ||