Redox driven B₁₂-ligand switch drives CarH photoresponse.

ABSTRACT: CarH is a coenzyme B₁₂-dependent photoreceptor involved in regulating carotenoid biosynthesis. How light-triggered cleavage of the B₁₂ Co-C bond culminates in CarH tetramer dissociation to initiate transcription remains unclear. Here, a series of crystal structures of the CarH B₁₂-binding domain after illumination suggest formation of unforeseen intermediate states prior to tetramer dissociation. Unexpectedly, in the absence of oxygen, Co-C bond cleavage is followed by reorientation of the corrin ring and a switch from a lower to upper histidine-Co ligation, corresponding to a pentacoordinate state. Under aerobic conditions, rapid flash-cooling of crystals prior to deterioration upon illumination confirm a similar B₁₂-ligand switch occurs. Remova

SUBMITTER: Poddar H 

PROVIDER: S-EPMC10442372 | biostudies-literature | 2023 Aug

REPOSITORIES: biostudies-literature