Curated Optogenetic Publication Database

Search precisely and efficiently by using the advantage of the hand-assigned publication tags that allow you to search for papers involving a specific trait, e.g. a particular optogenetic switch or a host organism.

Showing 1 - 2 of 2 results
1.

B12-based photoreceptors: from structure and function to applications in optogenetics and synthetic biology.

green Cobalamin-binding domains Review
Curr Opin Struct Biol, 6 Mar 2019 DOI: 10.1016/j.sbi.2019.01.020 Link to full text
Abstract: Vitamin B12-based photoreceptor proteins sense ultraviolet (UV), blue or green light using 5'-deoxyadenosylcobalamin (AdoCbl). The prototype of this widespread bacterial photoreceptor family, CarH, controls light-dependent gene expression in photoprotective cellular responses. It represses transcription in the dark by binding to operator DNA as an AdoCbl-bound tetramer, whose disruption by light relieves operator binding to allow transcription. Structures of the 'dark' (free and DNA-bound) and 'light' CarH states and studies on the unusual AdoCbl photochemistry have provided fundamental insights into these photoreceptors. We highlight these, the plasticity within a conserved mode of action among CarH homologs, their distribution, and their promising applications in optogenetics and synthetic biology.
2.

Plasticity in oligomerization, operator architecture, and DNA binding in the mode of action of a bacterial B12-based photoreceptor.

green Cobalamin-binding domains Background
J Biol Chem, 27 Sep 2018 DOI: 10.1074/jbc.ra118.004838 Link to full text
Abstract: Newly discovered bacterial photoreceptors called CarH sense light by using 5'-deoxyadenosylcobalamin (AdoCbl). They repress their own expression and that of genes for carotenoid synthesis by binding in the dark to operator DNA as AdoCbl-bound tetramers, whose light-induced disassembly relieves repression. High-resolution structures of Thermus thermophilus CarHTt have provided snapshots of the dark and light states and have revealed a unique DNA-binding mode whereby only three out of four DNA binding domains contact an operator comprising three tandem direct repeats. To gain further insights into CarH photoreceptors and employing biochemical, spectroscopic, mutational and computational analyses, here we investigated CarHBm from Bacillus megaterium We found that apoCarHBm, unlike monomeric apoCarHTt, is an oligomeric molten globule that forms DNA-binding tetramers in the dark only upon AdoCbl binding, which requires a conserved W-x9-EH motif. Light relieved DNA binding by disrupting CarHBm tetramers to dimers, rather than to monomers as with CarHTt CarHBm operators resembled that of CarHTt, but were larger by one repeat and overlapped with the -35 or -10 promoter elements. This design persisted in a six-repeat, multipartite operator we discovered upstream of a gene encoding an Spx global redox-response regulator whose photoregulated expression links photooxidative and general redox responses in B. megaterium Interestingly, CarHBm recognized the smaller CarHTt operator, revealing an adaptability possibly related to the linker bridging the DNA- and AdoCbl-binding domains. Our findings highlight a remarkable plasticity in the mode of action of B12-based CarH photoreceptors, important for their biological functions and development as optogenetic tools.
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