Movie
Controller
Structure viewers
About Yorodumi Papers
+Search query
-Structure paper
| Title | Chemical Mechanism of Allosteric and Asymmetric Dark Reversion in a Bacterial Phytochrome Uncovered by Cryo-EM. |
|---|---|
| Journal, issue, pages | J Am Chem Soc, Vol. 147, Issue 49, Page 45701-45711, Year 2025 |
| Publish date | Dec 10, 2025 |
 Authors | Szabolcs Bódizs / Anna-Lena M Fischer / Miklós Cervenak / Sayan Prodhan / Michal Maj / Sebastian Westenhoff /  |
| PubMed Abstract | Phytochromes are light-sensitive proteins that are found in plants, fungi, and bacteria. They exist in two functional states, Pr and Pfr, distinguished by / isomers of their bilin chromophore. The ...Phytochromes are light-sensitive proteins that are found in plants, fungi, and bacteria. They exist in two functional states, Pr and Pfr, distinguished by / isomers of their bilin chromophore. The chromophore can photoswitch between these states but also thermally converts in darkness. Despite the importance of the latter reaction, it is unknown how it is controlled by the phytochrome's structure. Here, we present single-particle cryo-EM measurements on the bacteriophytochrome (PaBphP) carried out at multiple time points during dark reversion from Pr to Pfr. These experiments resolved the structure of a PrPfr hybrid state as a transient intermediate. Surprisingly, we find that only protomer B converts back to Pfr in the hybrid, while protomer A remains in Pr. We identify structural asymmetries in the precursor Pr state, which extend from the homodimer interface to a conserved histidine (H277). The hydrogen-bonding network around the chromophore is modulated, explaining how a phytochrome exerts control over the isomerization reaction. These findings establish that dark reversion is governed by conformational selection between two substates, whereby one is "dark-reversion ready" and the other blocks the reaction. Moreover, we explain how the equilibrium of the states is allosterically controlled across the dimer. Together, these findings provide a structural framework for tuning phytochrome signaling lifetimes in optogenetic applications. |
 External links | J Am Chem Soc / PubMed:41317121 / PubMed Central |
| Methods | EM (single particle) |
| Resolution | 2.8 - 2.87 Å |
| Structure data |  EMDB-53913: Consensus reconstruction of the PrPfr hybrid state of the Pseudomonas aeruginosa bacteriophytochrome / PaBphP  EMDB-53914: Focus map on protomer A of the PrPfr hybrid state of the Pseudomonas aeruginosa bacteriophytochrome / PaBphP  EMDB-53915: Focused reconstruction of protomer B of the PrPfr hybrid state of the Pseudomonas aeruginosa bacteriophytochrome / PaBphP EMDB-53916, PDB-9rcc: |
| Chemicals |  ChemComp-LBV: |
| Source |
|
 Keywords | CYTOSOLIC PROTEIN / Phytochrome / Bacteriophytochrome / Photoreceptor / Histidine kinase |
pseudomonas aeruginosa (bacteria)