Abstract
Living organisms sense and respond to light, a crucial environmental factor, using photoreceptors, which rely on bound chromophores such as retinal, flavins, or linear tetrapyrroles for light sensing. The discovery of photoreceptors that sense light using 5'-deoxyadenosylcobalamin, a form of vitamin B12 that is best known as an enzyme cofactor, has expanded the number of known photoreceptor families and unveiled a new biological role of this vitamin. The prototype of these B12-dependent photoreceptors, the transcriptional repressor CarH, is widespread in bacteria and mediates light-dependent gene regulation in a photoprotective cellular response. CarH activity as a transcription factor relies on the modulation of its oligomeric state by 5'-deoxyadenosylcobalamin and light. This review surveys current knowledge about these B12-dependent photoreceptors, their distribution and mode of action, and the structural and photochemical basis of how they orchestrate signal transduction and control gene expression.
Keywords:
CarH; chromophore; optogenetics; photochemistry; photoregulation; transcriptional repressor.
Publication types
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Review
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Bacillus megaterium / genetics
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Bacillus megaterium / metabolism
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Bacillus megaterium / radiation effects
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Bacterial Proteins / chemistry*
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Bacterial Proteins / genetics
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Bacterial Proteins / metabolism
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Cobamides / chemistry
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Cobamides / metabolism*
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Gene Expression Regulation, Bacterial*
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Light
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Models, Molecular
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Myxococcus xanthus / genetics
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Myxococcus xanthus / metabolism
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Myxococcus xanthus / radiation effects
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Photochemistry
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Photoreceptors, Microbial / chemistry*
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Photoreceptors, Microbial / genetics
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Photoreceptors, Microbial / metabolism
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Protein Conformation
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Repressor Proteins / chemistry*
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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Signal Transduction
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Thermus thermophilus / genetics
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Thermus thermophilus / metabolism
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Thermus thermophilus / radiation effects
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Transcription Factors / chemistry*
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Transcription Factors / genetics
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Transcription Factors / metabolism
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Transcription, Genetic
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Vitamin B 12 / chemistry
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Vitamin B 12 / metabolism
Substances
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Bacterial Proteins
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Cobamides
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Photoreceptors, Microbial
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Repressor Proteins
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Transcription Factors
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cobamamide
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Vitamin B 12