8C37

An intermediate light exposed 2.15 Angstrom crystal structure of H132A variant of cobalamin binding domain belonging to a light-dependent transcription regulator TtCarH obtained under anaerobic conditions

Summary for 8C37

• Entry DOI: 10.2210/pdb8c37/pdb
• Descriptor: Probable transcriptional regulator, COBALAMIN (3 entities in total)
• Functional Keywords: carh, cobalamin, light-activated, transcription regulator, anaerobic, transcription
• Biological source: Thermus thermophilus
• Total number of polymer chains: 4
• Total formula weight: 98092.34

Authors

Poddar, H.,Leys, D. (deposition date: 2022-12-23, release date: 2023-08-16, Last modification date: 2023-08-30)

Primary citation

Poddar, H.,Rios-Santacruz, R.,Heyes, D.J.,Shanmugam, M.,Brookfield, A.,Johannissen, L.O.,Levy, C.W.,Jeffreys, L.N.,Zhang, S.,Sakuma, M.,Colletier, J.P.,Hay, S.,Schiro, G.,Weik, M.,Scrutton, N.S.,Leys, D.
Redox driven B 12 -ligand switch drives CarH photoresponse.
Nat Commun, 14:5082-5082, 2023

PubMed Abstract: CarH is a coenzyme B-dependent photoreceptor involved in regulating carotenoid biosynthesis. How light-triggered cleavage of the B Co-C bond culminates in CarH tetramer dissociation to initiate transcription remains unclear. Here, a series of crystal structures of the CarH B-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 B-ligand switch occurs. Removal of the upper His-ligating residue prevents monomer formation upon illumination. Combined with detailed solution spectroscopy and computational studies, these data demonstrate the CarH photoresponse integrates B photo- and redox-chemistry to drive large-scale conformational changes through stepwise Co-ligation changes.

PubMed: 37604813
DOI: 10.1038/s41467-023-40817-6

Experimental method

X-RAY DIFFRACTION (2.15 Å)