PDBsum entry 2byc

Signaling protein

PDB id: 2byc

Contents

Protein chains

137 a.a. *

Ligands

FMN ×2

Waters ×102

* Residue conservation analysis

PDB id:

2byc

Name:

Signaling protein

Title:

Blrb - a bluf protein, dark state structure

Structure:

Blue-light receptor of the bluf-family. Chain: a, b. Synonym: blrb, blue light sensing. Engineered: yes

Source:

Rhodobacter sphaeroides. Organism_taxid: 1063. Expressed in: escherichia coli. Expression_system_taxid: 469008.

Resolution:

1.90Å R-factor: 0.234 R-free: 0.288

Authors:

A.Jung,T.Domratcheva,M.Tarutina,Q.Wu,W.H.Ko,R.L.Shoeman,M.Gomelsky, K.H.Gardner,I.Schlichting

Key ref:

A.Jung et al. (2005). Structure of a bacterial BLUF photoreceptor: insights into blue light-mediated signal transduction. Proc Natl Acad Sci U S A, 102, 12350-12355. PubMed id: 16107542 DOI: 10.1073/pnas.0500722102

Date:

29-Jul-05 Release date: 24-Aug-05

Protein chains

Q3IYE4  (Q3IYE4_RHOS4) -  Blue-light receptor of the BLUF-family from Cereibacter sphaeroides (strain ATCC 17023 / DSM 158 / JCM 6121 / CCUG 31486 / LMG 2827 / NBRC 12203 / NCIMB 8253 / ATH 2.4.1.)

Seq: 140 a.a.

Struc: 137 a.a.*

* PDB and UniProt seqs differ at 1 residue position (black cross)

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1073/pnas.0500722102

Proc Natl Acad Sci U S A 102:12350-12355 (2005)

PubMed id: 16107542

Structure of a bacterial BLUF photoreceptor: insights into blue light-mediated signal transduction.

A.Jung, T.Domratcheva, M.Tarutina, Q.Wu, W.H.Ko, R.L.Shoeman, M.Gomelsky, K.H.Gardner, I.Schlichting.

ABSTRACT

Light is an essential environmental factor, and many species have evolved the capability to respond to it. Blue light is perceived through three flavin-containing photoreceptor families: cryptochromes, light-oxygen-voltage, and BLUF (sensor of blue light using flavin adenine dinucleotide, FAD) domain proteins. BLUF domains are present in various proteins from Bacteria and lower Eukarya. They are fully modular and can relay signals to structurally and functionally diverse output units, most of which are implicated in nucleotide metabolism. We present the high resolution crystal structure of the dark resting state of BlrB, a short BLUF domain-containing protein from Rhodobacter sphaeroides. The structure reveals a previously uncharacterized FAD-binding fold. Along with other lines of evidence, it suggests mechanistic aspects for the photocycle that is characterized by a red-shifted absorbance of the flavin. The isoalloxazine ring of FAD binds in a cleft between two helices, whereas the adenine ring points into the solvent. We propose that the adenine ring serves as a hook mediating the interaction with its effector/output domain. The structure suggests a unique photochemical signaling switch in which the absorption of light induces a structural change in the rim surrounding the hook, thereby changing the protein interface between BLUF and the output domain.

Selected figure(s)

Figure 1.
Fig. 1. Spectroscopic characterization of BlrB dark and signaling active states. (A) UV-visible absorption spectra of dark state (black line) and signaling state (red line) of BlrB recorded at 4°C. (B) 1H NMR spectra for the methyl regions of BlrB recorded under dark, signaling (lit), and postillumination dark states.

Figure 2.
Fig. 2. Structure and active site of BlrB. (A) The asymmetric unit of BlrB crystals contains two BlrB molecules with ferredoxin-like topology (apoproteins in gray and flavin cofactors in green). Secondary structure elements are assigned in molecule A (Left). (B) The flavin-binding pocket, shown in stereoview, is made up by the highest conserved residues of the BLUF domain. They position the cofactor by mostly hydrophobic interactions around the dimethylbenzene moiety and by hydrogen bonds to heteroatoms of the light absorbing ring system and the ribityl chain. Compared to most residues building up the cofactor pocket, the side chain of Arg-32 is less well defined. There is only a clear interaction with the O4' and O2 atoms of the flavin in molecule A. Hydrogen bonds are indicated by dotted lines, and distances are given in angstroms.

Figures were selected by an automated process.