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 a nitrogen-oxygen atom pair in sidechains of (Arg,Lys)-(Asp,Glu) are ≤ 4.0 Å apart<ref>PMID: 12202384</ref>. <!--The center of charge of the arginine sidechain is the zeta carbon<ref | A salt bridge is generally considered to exist when a nitrogen-oxygen atom pair in sidechains of (Arg,Lys)-(Asp,Glu) are ≤ 4.0 Å apart<ref name='KN2002'>PMID: 12202384</ref>. <!--The center of charge of the arginine sidechain is the zeta carbon<ref >PMID: 10449714</ref>.--> The nitrogen cation could also be the amino-terminus of a protein chain. The energetic significance of such complementary charge pairs is a complex function of the local environment<ref name='KN2002' />. | ||
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>. | 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>. | ||
