A New Facet of Vitamin B12: Gene Regulation by Cobalamin-Based Photoreceptors

Annu Rev Biochem. 2017 Jun 20:86:485-514. doi: 10.1146/annurev-biochem-061516-044500.

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

  • Review
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacillus megaterium / genetics
  • Bacillus megaterium / metabolism
  • Bacillus megaterium / radiation effects
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Cobamides / chemistry
  • Cobamides / metabolism*
  • Gene Expression Regulation, Bacterial*
  • Light
  • Models, Molecular
  • Myxococcus xanthus / genetics
  • Myxococcus xanthus / metabolism
  • Myxococcus xanthus / radiation effects
  • Photochemistry
  • Photoreceptors, Microbial / chemistry*
  • Photoreceptors, Microbial / genetics
  • Photoreceptors, Microbial / metabolism
  • Protein Conformation
  • Repressor Proteins / chemistry*
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Signal Transduction
  • Thermus thermophilus / genetics
  • Thermus thermophilus / metabolism
  • Thermus thermophilus / radiation effects
  • Transcription Factors / chemistry*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription, Genetic
  • Vitamin B 12 / chemistry
  • Vitamin B 12 / metabolism

Substances

  • Bacterial Proteins
  • Cobamides
  • Photoreceptors, Microbial
  • Repressor Proteins
  • Transcription Factors
  • cobamamide
  • Vitamin B 12