VHL possesses a RING domain, which is required for attachment of this substance to its targets.   
The importance of this substance in disease is shown in Von Hippel-Lindau syndrome, in which a  mutation in the VHL gene eliminates its ability to attach this substance to HIF-1 alpha, leading to cancer. VHL possesses a RING domain, which is required for attachment of this substance to its targets.   Consisting of 76 amino acids, it modifies its protein substrates at lysine residues, and is mediated by the enzymatic action of three ligases E1 through E3.  FTP, name this small protein whose primary function is to tag proteins. marking them for destruction by the proteasome, which is named for its presence in all eukaryotic cells.
The importance of this substance in disease is shown in Von Hippel-Lindau syndrome, in which a  mutation in the VHL gene eliminates its ability to attach this substance to HIF-1 alpha, leading to cancer.
ubiquitin