Source:
Generated By: https://synbiohub.org/public/igem/igem2sbol/1
Created by: Claudia Ivonne Hernandez Armenta
Date created: 2010-10-21 11:00:00
Date modified: 2015-05-08 01:12:12
J23105 constitutive promoter + LovTAP Photosensor
| Types | DnaRegion |
| Roles | Device engineered_region |
| Sequences | BBa_K360127_sequence (Version 1) |
Description
This photoreceptor was assembled by Strickland et al., and consists of a LOV (light-oxygen-voltage) domain of Avena sativa phototropin1 (AsLOV2) that senses blue light, fused to the trpR- DNA binding domain of the transcription factor trp repressor. The resulting protein is called LovTAP: LOV- and tryptophan-activated protein.LOV domains bind a flavin-mononucleotide (FMN) or flavin-adenine-dinucleotide (FAD) cofactor, which are used in a wide variety of metabolic pathways as cofactors in redox reactions and are available in most organisms. The cofactor has a broad absorption spectrum, with a maximum at 450 nm. Besides, the core of the LOV domain is often flanked by amino- or carboxy-terminal helices, termed A???α and Jα, respectively.
In the LovTAP construction, AsLOV2 domain via its carboxyl-terminal Jα ???helix was ligated to an amino-terminal truncation of TrpR. The resulting protein has a domain-domain overlap with a shared helix. Thus, photoexcitation would change the conformation of the protein, in turn changing the stability of the shared-helix-domain contacts.
Under the presence of light, absorption of a photon leads to the formation of a covalent adduct between the flavin mononucleotide (FMN) cofactor and a conserved cysteine residue in the AsLOV2 domain, which results in conformational rearrangements in LovTAP. This change impacts the affinity of the shared helix for the two domains: disrupting the contacts between the shared helix and the LOV domain and enabling the association of the shared helix with the TrpR domain, which establishes DNA-binding affinity and LovTAP can then bind DNA as an homodimer, repressing the transcription of the genes downstream of its binding sites.
In the dark, when the shared helix contacts the LOV domain, the TrpR domain's DNA-binding affinity decreases and LovTAP is in an inactive conformation.
Notes
noneSource
none| Access | Instance | Definition |
| public public | BBa_J23105 BBa_K360121 | BBa_J23105 BBa_K360121 |
| Sequence Annotation | Location | Component / Role(s) |
| BBa_J23105 BBa_K360121 | 1,35 44,887 | BBa_J23105 BBa_K360121 |