Patent ID: 6890745

Claim:
A purified polypeptide characterized as having Renilla luciferase activity and a recognition site specifically cleavable by a protease, wherein cleavage results in a decrease in luciferase activity and wherein the recognition site is at residues 197-200 of SEQ ID NO:2, wherein the recognition site is a peptide sequence selected from the group consisting of DEVD (SEQ ID NO: 21), VEHD (SEQ ID NO: 23, wherein X is H), LETD (SEQ ID NO: 24) LEHD (SEQ ID NO: 22, wherein X is L or SEQ ID NO: 25) IEPD (SEQ ID NO: 16), DETD (SEQ ID NO: 17), WEHD (SEQ ID NO: 22, wherein X is W or SEQ ID NO: 18), YVAD (SEQ ID NO: 19), VEID (SEQ ID NO: 23, wherein X is I), and any combination thereof.