Isopeptide bond: Difference between revisions
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==Formation== | ==Formation== | ||
==Spontaneous== | ==Spontaneous== | ||
Some isopeptide bonds appear to form spontaneously during protein folding. These include the intramolecular isopeptide bonds in pilin monomers<ref name="kang2009" />, and the "chain mail" isopeptide bonds in the capsid of bacteriophate HK97. | Some isopeptide bonds appear to form spontaneously during protein folding. These include the intramolecular isopeptide bonds in pilin monomers<ref name="kang2009" />, and the "chain mail" isopeptide bonds in the capsid of bacteriophate HK97<ref name="wikoff2000" />. | ||
===Enzymatic=== | ===Enzymatic=== | ||
Inter-molecular isopeptide bonds that link bacterial pilins into lengthy pili are formed enzymatically by a cysteine transpeptidase "sortase"<ref name="kang2009">PMID: 19497855</ref>. However, the same pilins have multiple intra-molecular isopeptide bonds that appear to form spontaneously<ref name="kang2009" />. | Inter-molecular isopeptide bonds that link bacterial pilins into lengthy pili are formed enzymatically by a cysteine transpeptidase "sortase"<ref name="kang2009">PMID: 19497855</ref>. However, the same pilins have multiple intra-molecular isopeptide bonds that appear to form spontaneously<ref name="kang2009" />. | ||
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==Examples== | ==Examples== | ||
*The capsid of the HK97 bacteriophage contains isopeptide bonds that cross-link the protein [[chains]] into a protein ''chain mail'' <ref>PMID: 22297521</ref><ref>PMID: 10572124</ref><ref>PMID: 19091865</ref>. However, these do not occur in the [[asymmetric unit]] of [[1ohg]]<ref>PMID: 11000116</ref>. They can be visualized in the [[biological unit]], which is the full virus capsid, but that is technically challenging. | *The capsid of the HK97 bacteriophage contains isopeptide bonds that cross-link the protein [[chains]] into a protein ''chain mail'' <ref>PMID: 22297521</ref><ref>PMID: 10572124</ref><ref name="wikoff2000">PMID: 19091865</ref>. However, these do not occur in the [[asymmetric unit]] of [[1ohg]]<ref>PMID: 11000116</ref>. They can be visualized in the [[biological unit]], which is the full virus capsid, but that is technically challenging. | ||
* [[7cap]] is a ubiquitin homotrimer. The C-terminal Gly76 is isopeptide linked to Lys48 in each inter-chain interface<ref>PMID: 32731397</ref>. | * [[7cap]] is a ubiquitin homotrimer. The C-terminal Gly76 is isopeptide linked to Lys48 in each inter-chain interface<ref>PMID: 32731397</ref>. | ||
* [[4mli]] contains the SpyTag peptide (which can be linked to a protein of interest) forming an isopeptide bond between SpyTag peptide Lys31 and SpyCatcher protein Asp117<ref>PMID: 24161952</ref>. | * [[4mli]] contains the SpyTag peptide (which can be linked to a protein of interest) forming an isopeptide bond between SpyTag peptide Lys31 and SpyCatcher protein Asp117<ref>PMID: 24161952</ref>. | ||
