Toolkit Items

Aureochrome-1 (AUREO1) is a blue-light receptor from Vaucheria frigida with an N-terminal bZIP DNA-binding domain and a C-terminal LOV photosensory domain. Full-length AUREO1 binds DNA in a sequence-specific manner, and light signaling is transmitted from the LOV core via the hydrophobic region of the LOV β-sheet surface.

The A'α-helix is an N-terminal upstream element of the Arabidopsis thaliana phototropin1 LOV2 photosensory module that interacts with the Jα-helix and contributes to blue-light signal transmission to the downstream serine/threonine kinase. Truncation of this region or Ala substitution of conserved A'α/Aβ-gap residues Glu474 and Lys475 impairs blue-light-induced kinase activation in phot1 LOV2-STK polypeptides.

The Escherichia coli YcgF protein contains a C-terminal EAL domain linked to an N-terminal FAD-binding BLUF photosensory domain. In this full-length blue-light-responsive protein context, the EAL domain is predicted to have cyclic-di-GMP phosphodiesterase activity.

Microscopy is a protocolized assay method included alongside fluorescent polarization and phage display in a 2020 methods source on engineering and applying LOV2-based photoswitches. In that context, it is used as part of the experimental workflow for validating, improving, and using light-responsive optogenetic switches built on the LOV2 domain.

YcgF (Blrp) is an Escherichia coli full-length blue-light sensing protein that contains an N-terminal FAD-binding BLUF domain and a C-terminal EAL domain. It functions as a BLUF-family photoreceptor in which the FAD chromophore undergoes light-responsive changes, and spectroscopy indicates coupling between the BLUF photochemistry and structural responses in the full-length protein.

The A'α/Aβ gap is a structurally defined region N-terminal to the LOV2 core of Arabidopsis thaliana phototropin1. In LOV2-serine/threonine kinase polypeptides, this region contributes to blue-light signal transmission from LOV2 to kinase activation, and conserved residues Glu474 and Lys475 are required for efficient light-induced kinase activation.

The AUREO1 LOV-only construct is an isolated LOV photosensory domain derived from aureochrome-1. In the cited study, blue light induced a secondary-structure shift from increased alpha-helical to increased beta-sheet character in this LOV-only construct without a detectable change in hydrodynamic radius.

The Jα-helix of LOV2 is a C-terminal helix located downstream of the LOV2 domain in Arabidopsis phototropin1. Evidence from blue-light-dependent trypsin digestion indicates that this helix undergoes a light-responsive structural change and participates in intramolecular signal transmission toward the kinase region.

The full-length AUREO1 construct is a blue-light-responsive transcription factor from Vaucheria frigida that contains an N-terminal bZIP domain and a C-terminal LOV domain. In the reported study, the full-length protein binds DNA in a sequence-specific manner and undergoes an approximately 5% blue-light-induced increase in hydrodynamic radius.

Since crystal structures of both phytochromes are known, the phytochrome system of A. fabrum provides a tool for following the entire signal transduction cascade starting from light induced conformational changes to protein interaction and the triggering of DNA transfer processes.