Patent ID: 7781182

Claim:
A method of assaying ubiquitin ligase activity comprising: a) combining: i) tag1-ubiquitin, wherein the ubiquitin has at least 95% sequence identity to the amino acid sequence provided in SEQ ID NO: 13, or is encoded by a nucleotide sequence having at least 95% sequence identity to the nucleotide sequence depicted in an accession number selected from the group consisting of M26880 (SEQ ID NO: 22) and AB003730 (SEQ ID NO: 23); ii) ubiquitin activating enzyme (E1); iii) ubiquitin conjugating enzyme (E2); iv) tag2-ubiquitin ligase (E3); b) measuring the amount of said tag1-ubiquitin bound to said ubiquitin ligase (E3), whereby the amount of said tag1-ubiquitin bound to said ubiquitin ligase (E3) indicates said ubiquitin ligase activity.