Figure 1. The CreLite system.

The light inducible protein binding pair, truncated Phytochrome B (PhyBΔ) and the active protein binding domain of Phytochrome B interacting factor 6 (PIF6APB) are fused with C-terminus Cre (CreC) and N-terminus Cre (CreN), respectively. A cofactor analog, phycocyanobilin (PCB), is required for PhyBΔ to be functional. Once exposed to red light (λ_max = 650 nm), the PhyBΔ and PIF6APB bind each other and bring the two halves of Cre together, resuming its recombinase activity.