Patent ID: 7588907

Claim:
A method of detecting covalent modification of a protein, comprising: a) providing i) a first fusion protein comprising a first fragment of a fluorescent protein linked to ubiquitin, wherein said first fragment of a fluorescent protein is selected from the group consisting of SEQ ID NOs: 3, 5, 9, and 10; and ii) a second fusion protein comprising a second fragment of said fluorescent protein linked to said protein of interest, wherein said second fragment of a fluorescent protein is selected from the group consisting of SEQ ID NOs: 2, 4,6,7,8, and 11; and b) contacting said first and second fragments of said fluorescent protein under conditions such that said first and second fragments of said fluorescent protein re-associate to form a fluorescent protein that generates a optically detectable signal in the presence but not the absence of covalent modification of said protein of interest by said ubiquitin of said first fusion protein.