Table 1.
Comparison of optogenetic systems.
| Protein domain | Chromophore | Stimulus and time | Forward reaction | Reversibility and time | Demonstrated applications |
|---|---|---|---|---|---|
| UVR8 | Tryptophan | 300 nm, subsecond | Homodimer to monomer then heterodimer with COP1 | Negligible in non-plant cells | Release of membrane cargo from aggregates in ER, transcription |
| BLUF | FAD | 450 nm, subsecond | Conformational change | Spontaneous, ∼3 (euPACα) or 19 s (bPAC) | Activation of naturally linked adenylate cyclase |
| phototropin LOV2 | FMN | 450 nm, subsecond | Jα helix bound to unbound | Spontaneous, ∼1 min∗ | Uncaging of fused peptide, activation of fused protein function |
| EL222 LOV-HTH | FMN | 450 nm, subsecond | Monomer to homodimer via HTH domain | Spontaneous, ∼1 min | Transcription |
| FKF1 LOV | FMN | 450 nm, minutes | Monomer to heterodimer with GIGANTEA | Spontaneous, days | Activation through membrane recruitment, transcription |
| VVD LOV | FAD | 450 nm, subsecond | Monomer to homodimer | Spontaneous, ∼5 h∗∗ | Transcription |
| CRY2 | FAD | 450 nm, subsecond | Monomer to homooligomer and complex with CIB1 | Spontaneous, minutes | Activation through oligomerization, membrane recruitment, or fragment assembly, inactivation through aggregation, transcription |
| miniSOG | FMN | 480 nm, minutes | Generate reactive oxygen species | Irreversible protein inactivation | Inactivating proteins through oxidizing adjacent residues |
| Dronpa K145N | GFP chromophore | 500 nm, seconds | Homotetramer to monomer | Spontaneous in minutes, or seconds with 400 nm | Caging and uncaging of proteins |
| Opsins | Retinal | 400–600 nm, minutes | Heteromer with GαGβγ to monomer | Negligible | Activation of G-protein effectors |
| PhyB | phyto-chromobilin | 650 nm, subsecond | Homodimer to complex with PIF | Spontaneous in minutes, or seconds with 700 nm | Activation through membrane recruitment, transcription |
Major characteristics of representative optogenetic systems, grouped by photosensory module and ordered by excitation wavelength. Indicated times are reaction half-times with typical illumination powers on a microscope, i.e., 0.1–10 W/cm2. ∗Tunable to ∼3 s to 17 min with mutations (Zoltowski et al., 2009). ∗∗Tunable to ∼30 s to 2 days with mutations (Zoltowski et al., 2009).