Table 1.

Non-associating engineered photoreceptors.

Class	Protein architecturea	Trade name	Cofactor	Size (aa)b	Activation/Deactivation λmax (nm)	Dark recoveryc	Optogenetic application
LOV	AsLOV2-EcTrpR	LOV-TAP	FMN	240	450/dark	Seconds	DNA binding (Strickland et al., 2008)
	AsLOV2 inserted into EcDHFR	–	FMN	300	450/dark	Seconds	Enzymatic activity (Lee et al., 2008)
	AsLOV2-HsRac1	PA-Rac1	FMN	320	450/dark	Seconds	GTPase signaling (Wu et al., 2009)
	AsLOV2-HsStim1	LOVS1K	FMN	360	450/dark	Seconds	Ion channel activation (Pham et al., 2011)
	AsLOV2-HsCaspase 7	L57V	FMN	400	450/dark	Seconds	Caspase/apoptosis (Mills et al., 2012)
	DaαDTX-AsLOV2	Lumitoxin	FMN	300	450/dark	Seconds	Ion channel inhibition (Schmidt et al., 2014)
	AtLOV2-MmOdc1 peptide	PSD	FMN	160	450/dark	Seconds	Protein degradation (Renicke et al., 2013)
	AsLOV2-peptide	B-LID	FMN	150	450/dark	Seconds	Protein degradation (Bonger et al., 2014)
	AsLOV2-HsPKI	PA-PKI	FMN	160	450/dark	Seconds	Inhibition of endogenous Ser/Thr kinases (Yi et al., 2014)
	AsLOV2-peptide	PA-MKI
	AsLOV2-peptides	LINuS	FMN	150	450/dark	Seconds	Nuclear transport (Niopek et al., 2014)
	BsYtvA-BjFixL	YF1, YHF	FMN	390	Dark/450	Minutes to hours	Prokaryotic gene expression (Möglich et al., 2009a, 2010a; Ohlendorf et al., 2012)
PYP	ScGCN4-HhPYP	–	pCA	160	450/dark	Seconds	DNA binding (Fan et al., 2011)
rhodopsin	BtRhodopsin-Cgβ2AR	–	Retinal	350	500/dark	Seconds to minutes	cNMP signaling (Kim et al., 2005)
	BtRhodopsin-Hsα1aAR BtRhodopsin-Cgβ2AR	OptoXR	Retinal	400 350	500 /dark	Seconds to minutes	cNMP and PLC signaling (Airan et al., 2009)
	MmMelanopsin CrOpsin	–	Retinal	500 330	480/lightd 500	Seconds Seconds	cNMP and PLC signaling (Karunarathne et al., 2013)
	MmMelanopsin-MmmGluR6	Opto-mGluR6	Retinal	500	480/lightd	Seconds	vision restoration (Van Wyk et al., 2015)
	RrRhodopsin-Hs5-HT1A	Rh-CT5-HT1A	Retinal	350	485/dark	Seconds to minutes	Ion-channel activation (Oh et al., 2010)
bacterio-phytochrome	SpCph1-EcEnvZ	Cph8	PCB	750	660/720	Minutes	Prokaryotic gene expression (Levskaya et al., 2005)
	DrBPhy-HsPDE2A	LAPD	BV	890	700/750	Minutes	cNMP hydrolysis (Gasser et al., 2014)
	RsBPhG-NsCyaB1	IlaC	BV	800	710/760	Minutes	cAMP formation (Ryu et al., 2014)

^aSpecies abbreviations as follows: As, Avena sativa; At, Arabidopsis thaliana; Bj, Bradyrhizobium japonicum; Bs, Bacillus subtilis; Bt, Bos taurus; Cg, Cricetulus griseus; Cr, Carybdea rastonii; Dr, Deinococcus radiodurans; Da, Dendroaspis angusticeps; Ec, Escherichia coli; Hh, Halorhodospira halophila; Hs, Homo sapiens; Mm, Mus musculus; Ns, Nostoc sp.; Rr, Rattus rattus; Rs, Rhodobacter sphaeroides; Sc, Saccharomyces cerevisiae; Sp, Synechocystis PCC6803; “peptide” refers to a short, synthetic sequence.

^bSizes are approximate.

^cTime scales refer to intrinsic dark-recovery reaction; note that this is temperature-dependent and may be followed by slow biological processes.

^dMelanopsin has been reported to be photochromic but the spectrum for deactivation has not been thoroughly determined (Ernst et al., 2014).