45TX

FAST-DM complex

This is a non-PDB format compatible entry.

Summary for 45TX

• Entry DOI: 10.2210/pdb45tx/pdb
• Related: 45SD
• Descriptor: FAST-DM, (5~{Z})-5-[(3,5-dimethyl-4-oxidanyl-phenyl)methylidene]-2-sulfanylidene-1,3-thiazolidin-4-one (3 entities in total)
• Functional Keywords: fluorescent protein, fret acceptor, ligand dependent fluorescence
• Biological source: synthetic construct
• Total number of polymer chains: 1
• Total formula weight: 13868.74

Authors

Nayak, S.R.,Singh, N.,Penmatsa, A.,Nair, D.K. (deposition date: 2026-09-09, release date: 2026-10-28)

Primary citation

Singh, N.,Nayak, S.R.,Mohanty, S.K.,Hanumantharaju, A.,Shaju, A.,Jose, M.,Penmatsa, A.,Nair, D.
Reversible, Chemically Gated FRET via Ligand-Activated Acceptors.
Adv Sci, :e77693-e77693, 2026

PubMed Abstract: Genetically encoded fluorogen-activating tags enable conditional fluorescence, yet the structural and excited-state mechanisms underlying ligand activation remain unclear. Here, we combine X-ray crystallography, computational modelling, and fluorescence lifetime imaging microscopy (FLIM) to define the structural and photophysical basis of fluorogen activation in the Fluorescence-Activating and Absorption-Shifting Tag (FAST). Structures of apo and ligand-bound FAST reveal the interface for fluorogen binding. In the apo state, N-terminal residues occlude the pocket, whereas ligand binding displaces these elements to generate a solvent-accessible cavity stabilized by ordered water molecules. Distinct hydroxybenzylidene rhodanine derivatives differentially tune interfacial geometry and excited-state ensembles, producing single or multiexponential fluorescence lifetimes in living cells that primarily reflect modulation of excited-state relaxation. Leveraging this ligand dependence, we utilize FAST as a chemically gated Förster resonance energy transfer (FRET) acceptor that induces reversible, concentration-dependent donor lifetime shortening that does not require additional external controls. Using ligand-controlled FLIM-FRET, we resolve supramodular organization within Membrane-Associated Guanylate Kinase (MAGUK) scaffolds in live cells, establishing FAST as a reversible photophysical module for mapping molecular architecture.

PubMed: 42801590
DOI: 10.1002/advs.77693

Experimental method

X-RAY DIFFRACTION (1.66 Å)