PDBsum entry 5c8f

Transcriptional regulator

PDB id: 5c8f

Contents

Protein chain

274 a.a.

Ligands

B12

GOL

Metals

_CL ×2

Waters ×19

PDB id:

5c8f

Name:

Transcriptional regulator

Title:

Crystal structure of light-exposed full-length thermus thermophilus carh bound to cobalamin

Structure:

Light-dependent transcriptional regulator carh. Chain: a. Engineered: yes

Source:

Thermus thermophilus (strain hb27 / atcc baa- 163 / dsm 7039). Organism_taxid: 262724. Strain: hb27 / atcc baa-163 / dsm 7039. Gene: tt_p0056. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.65Å R-factor: 0.174 R-free: 0.203

Authors:

M.Jost,C.L.Drennan

Key ref:

M.Jost et al. (2015). Structural basis for gene regulation by a B12-dependent photoreceptor. Nature, 526, 536-541. PubMed id: 26416754 DOI: 10.1038/nature14950

Date:

25-Jun-15 Release date: 30-Sep-15

Protein chain

Q746J7  (Q746J7_THET2) -  Probable transcriptional regulator from Thermus thermophilus (strain ATCC BAA-163 / DSM 7039 / HB27)

Seq: 285 a.a.

Struc: 274 a.a.

DOI no: 10.1038/nature14950

Nature 526:536-541 (2015)

PubMed id: 26416754

Structural basis for gene regulation by a B12-dependent photoreceptor.

M.Jost, J.Fernández-Zapata, M.C.Polanco, J.M.Ortiz-Guerrero, P.Y.Chen, G.Kang, S.Padmanabhan, M.Elías-Arnanz, C.L.Drennan.

ABSTRACT

Photoreceptor proteins enable organisms to sense and respond to light. The newly discovered CarH-type photoreceptors use a vitamin B12 derivative, adenosylcobalamin, as the light-sensing chromophore to mediate light-dependent gene regulation. Here we present crystal structures of Thermus thermophilus CarH in all three relevant states: in the dark, both free and bound to operator DNA, and after light exposure. These structures provide visualizations of how adenosylcobalamin mediates CarH tetramer formation in the dark, how this tetramer binds to the promoter -35 element to repress transcription, and how light exposure leads to a large-scale conformational change that activates transcription. In addition to the remarkable functional repurposing of adenosylcobalamin from an enzyme cofactor to a light sensor, we find that nature also repurposed two independent protein modules in assembling CarH. These results expand the biological role of vitamin B12 and provide fundamental insight into a new mode of light-dependent gene regulation.