Luciferase biosensors for cAMP

1. A polynucleotide encoding a modified luciferase comprising luciferase sequences and a heterologous amino acid sequence for a mutant RIIβB cAMP binding site inserted at a site or region in the luciferase that is tolerant to modification, wherein the luciferase sequences in the modified luciferase are circularly permuted relative to a wild-type luciferase and are firefly luciferase sequences, wherein the permutation is in a region corresponding to residue 2 to 12, residue 32 to 53, residue 70 to 88, residue 102 to 126, residue 139 to 165, residue 183 to 203, residue 220 to 247, residue 262 to 273, residue 303 to 313, residue 353 to 408, residue 485 to 495, or residue 535 to 546 of SEQ ID NO: 106, 118, or 120, wherein the mutant RIIβB cAMP binding site has at least 80% amino acid sequence identity to the cAMP binding site of residue 266-414 of SEQ ID NO: 4, wherein the cAMP binding site is in a region corresponding to residue 2 to 12, residue 32 to 53, residue 70 to 88, residue 102 to 126, residue 139 to 165, residue 183 to 203, residue 220 to 247, residue 262 to 273, residue 303 to 313, residue 353 to 408, residue 485 to 495, or residue 535 to 546 of SEQ ID NO: 106, 118, or 120, wherein binding of cAMP to the mutant RIIβB cAMP binding site produces a response from the modified luciferase, wherein the mutant RIIβB cAMP binding site has one or more substitutions that enhance the luminescence signal of the modified luciferase, enhance the response of the modified luciferase to a change in the amount of cAMP in a cell, reduce affinity of wild-type cAMP binding, or a combination thereof, relative to a corresponding luciferase with a RIIβB cAMP binding site that lacks the one or more substitutions, wherein one or more of the substitutions are at a position corresponding to residue 266, 282, 284, 286, 296, 316, 333, 338, 382, 389, 404, or 407 of RIIβB having SEQ ID NO: 4.

2. The polynucleotide of claim 1 wherein the mutant cAMP binding site is flanked by a peptide linker.

3. The polynucleotide of claim 2 wherein the peptide linker comprises GSSGGSGGSGGG (SEQ ID NO:41), GSSSDSDSSAGS (SEQ ID NO:42), GSNDSSGGSEGG (SEQ ID NO:43), GSNGGFDSSEGG (SEQ ID NO:44), GSIRWSGLSGGD (SEQ ID NO:45), GSRGGSVYSEGG (SEQ ID NO:46), GSSEGSSDFGGD (SEQ ID NO:47), GSIWSCSSEGG (SEQ ID NO:48), GSNWDSGCSREG (SEQ ID NO:49), GSNWDSGCSREC (SEQ ID NO:50), GSSGCTGDAGGS (SEQ ID NO:51), GSNWDSGCSRQC (SEQ ID NO:52), GSS/NS/D/GD/S/GS/FD/GS/GSA/EGS/G (SEQ ID NO:53), GSI/R/SR/G/EW/GSG/V/SL/Y/DS/FG/EGD/G (SEQ ID NO:54), GSI/N/SV/W/GV/D/CS/TC/GS/C/DS/AE/R/GG/EG/S (SEQ ID NO:55), GSI/SV/G/AV/GS/CG/DG/D/SS/AG/EG/EG/N (SEQ ID NO:56), GSI/N/SV/W/G/AV/D/C/GS/T/CC/GS/C/DS/AE/R/GG/EG/S (SEQ ID NO:57), GSIAGCGDAGEG (SEQ ID NO:126), GSNWDSGCSRE (SEQ ID NO: 127), GSNWDSGCSREG (SEQ ID NO:129), NWDSGCSREG (SEQ ID NO: 130), or IAGCGDAGEG (SEQ ID NO: 131).

4. A vector comprising the polynucleotide of claim 1 .

5. A polypeptide encoded by the polynucleotide of claim 1 .

6. A fusion protein comprising the polypeptide of claim 5 .

7. A method to detect changes in cAMP amount or concentration in a cell, comprising:

a) providing a sample comprising the polynucleotide of claim 1 and reagents for a luminescence reaction; and

b) detecting or determining luminescence in the mixture, thereby detecting or determining the amount or concentration of cAMP in the cell.