Thioester protein crosslinks

Thioester bonds between cysteine and glutamine sidechains can form covalent cross-links between polypeptide chains. Thioester bonds are one way that ubiquitin may be attached to proteins (ubiquitinylation; see also Ubiquitin and Ubiquitination). Thioester bonds in complement proteins C3 and C4 are involved in tagging pathogens for destruction by the immune system, via the alternate complement activation pathway. Thioester bonds occur in thioester domains (TED) of Gram-positive bacteria, where they are thought to mediate covalent adhesion of bacteria to host cells. Many surface proteins of Gram-positive bacteria are predicted to contain TED as well as isopeptide and ester cross-links. This family of proteins is termed TIE proteins for thioester, isopeptide, ester proteins. Examples: 2xi9, 6fwy.

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Other Protein Cross-LinksOther Protein Cross-Links

In addition to the thioester bonds discussed above, other covalent cross-links between polypeptide chains include:

• Disulfide bonds
• Isopeptide bonds
• Lysine-cysteine NOS bonds