Patent ID: 7973132
Filing Date: 2011-07-05
Classification: C07K,C12Q,G01N

Abstract:
1. An engineered fluorescent protein comprising: a) a fluorescent protein differing in amino acid sequence from the reference protein of (i) SEQ ID NO: 1-3 or 5, wherein the difference consists of substituting a glutamic acid or an aspartic acid with an arginine or a lysine at positions 17, 19, and 21 of SEQ ID NO:1-3 or 5, or (ii) SEQ ID NO: 4, wherein the difference consists of substituting a glutamic acid or an aspartic acid with an arginine or a lysine at positions 18, 20, and 22 of SEQ ID NO: 4, wherein the modified protein is permeable to a cell; b) a peptide linker region linked at either the amino or carboxyl end of the modified fluorescent protein, wherein the linker region is a polypeptide between about 1 and 30 amino acid residues in length and is susceptible to digestion by a cellular protease; and c) a fluorescence modifier moiety linked to the other end of the linker region, wherein a fluorescence resonance energy transfer occurs between the modified fluorescent protein and the fluorescence modified moiety in the uncleaved engineered fluorescent protein, and wherein when the protease cleaves the linker region of the engineered fluorescent protein in a cell, a change in fluorescence occurs in the cell as compared to a reference cell that contains the uncleaved engineered fluorescent protein, but not the cellular protease.