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Interacting with cells and proteins in a rapid and reversible way is one key program of optogenetics. But light can also be used to produce targeted lesions, an approach which can be relevant for perturbing neural circuits and designing models of neurodegenerative disorders. One way of making these lesions specific is to target light-sensitive molecules called photosensitizers (PSs) to particular proteins or cells. When irradiated with light, PSs generate reactive oxygen species (ROS) which very rapidly react with any nearby biomolecule and can eventually kill cells through apoptosis or necrosis. The technique, called chromophore-assisted light inactivation (CALI), has been used extensively for the treatment of precancerous lesions and superficial tumors (photodynamic therapy). Most available PSs are organic molecules which have to be introduced exogenously into living systems and offer very poor selectivity for particular cell types or proteins. One solution to this issue is to rely on peptide-like (peptoids) PSs which are resistant to proteolysis and can be designed to bind specifically to virtually any given protein [1]. But a more definitive solution for protein- and cell-type-specific CALI was the design of the first genetically encoded PS [2]. The protein called KillerRed was isolated by screening a collection of GFP homologs for phototoxic effects on E. coli cells. Although its ROS-production capacity is still inferior to chemical PSs, KillerRed has been used successfully in zebrafish embryos to induce cell death [3] and in cell cultures to achieve target protein inactivation [4] and reversible blockage of cell division [5].

Summary of available variants

Acronym Full Name Description GenBank link Refs
Killer-Red Killer-Red KillerRed is a GFP-related dimeric red fluorescent protein. It was isolated by screening GFP homologs for phototoxic effects in E. Coli. Killer-Red is a mutated version of the hydrozoan chromoprotein anm2CP. AY969116 [6]
H2B-tKR H2B-tKR is a tandem version of Killer-Red fused to histone H2B. It allows correct chromatin labeling and functioning in the dark, and blocks cell proliferation upon exposure to green light. [5]

Properties of available variants

Acronym Excitation peak (nm) Emission peak (nm) Property 3 Property 4 Refs
Killer-Red 585 610 [6]
H2B-tKR [5]

List of available constructs

Name Description Map Available from
Lab Company
pKillerRed-N pKillerRed-N is a mammalian expression vector encoding photosensitizer KillerRed. The vector allows generation of fusions to the KillerRed N-terminus and expression of KillerRed fusions or KillerRed alone in eukaryotic (mammalian) cells. Vector Information Evrogen


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  1. Error fetching PMID 20228793: [Lee2010]
  2. Error fetching PMID 16369538: [Bulina2006a]
  3. Error fetching PMID 21040591: [Teh2010]
  4. Error fetching PMID 17406328: [Bulina2006b]
  5. Error fetching PMID 21214518: [Serebrovskaya2011]
  6. Error fetching PMID 8146171: [Liao1994]
  7. Error fetching PMID 21214518: [Serebrovskaya]
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