The photochemical mechanism of a B12-dependent photoreceptor protein.
The coenzyme B12-dependent photoreceptor protein, CarH, is a bacterial transcriptional regulator that controls the biosynthesis of carotenoids in response to light. On binding of coenzyme B12 the monomeric apoprotein forms tetramers in the dark, which bind operator DNA thus blocking transcription. Under illumination the CarH tetramer dissociates, weakening its affinity for DNA and allowing transcription. The mechanism by which this occurs is unknown. Here we describe the photochemistry in CarH that ultimately triggers tetramer dissociation; it proceeds via a cob(III)alamin intermediate, which then forms a stable adduct with the protein. This pathway is without precedent and our data suggest it is independent of the radical chemistry common to both coenzyme B12 enzymology and its known photochemistry. It provides a mechanistic foundation for the emerging field of B12 photobiology and will serve to inform the development of a new class of optogenetic tool for the control of gene expression.
School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.|Photon Science Institute, The University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL, UK.|SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
Roger J
RJ
Kutta
SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.|Faculty of Life Sciences, The University of Manchester, Carys Bannister Building, Dover Street, Manchester M13 9PL, UK.
Samantha J O
SJO
Hardman
SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.|Faculty of Life Sciences, The University of Manchester, Carys Bannister Building, Dover Street, Manchester M13 9PL, UK.
Linus O
LO
Johannissen
School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.|SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
Bruno
B
Bellina
SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.|Faculty of Life Sciences, The University of Manchester, Carys Bannister Building, Dover Street, Manchester M13 9PL, UK.
Hanan L
HL
Messiha
Department of Genetics and Microbiology, Area of Genetics (Unidad Asociada al Instituto de Química Física-Consejo Superior de Investigaciones Científicas), Faculty of Biology, Universidad de Murcia, 30100 Murcia, Spain.
Juan Manuel
JM
Ortiz-Guerrero
Department of Genetics and Microbiology, Area of Genetics (Unidad Asociada al Instituto de Química Física-Consejo Superior de Investigaciones Científicas), Faculty of Biology, Universidad de Murcia, 30100 Murcia, Spain.
Montserrat
M
Elías-Arnanz
Instituto de Química Física 'Rocasolano', Consejo Superior de Investigaciones Científicas, 28006 Madrid, Spain.
S
S
Padmanabhan
School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.|SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
Perdita
P
Barran
SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.|Faculty of Life Sciences, The University of Manchester, Carys Bannister Building, Dover Street, Manchester M13 9PL, UK.
Nigel S
NS
Scrutton
School of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, UK.|Photon Science Institute, The University of Manchester, Alan Turing Building, Oxford Road, Manchester M13 9PL, UK.|SYNBIOCHEM, Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, UK.
Alex R
AR
Jones
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002845:Chromatography; D003038:Cobamides / Q000737:chemistry / Q000378:metabolism*; D003198:Computer Simulation; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D008027:Light; D008956:Models, Chemical; D008958:Models, Molecular; D055668:Photochemical Processes; D011487:Protein Conformation; D013057:Spectrum Analysis / Q000379:methods; D016963:Thermus thermophilus / Q000235:genetics / Q000378:metabolism*
D001426:Bacterial Proteins; D003038:Cobamides; C000913:cobamamide