Part:BBa_K660000

LOV2 Domain

Plants, fungi and bacteria are required to respond to light in order to induce responses. Such responses include blue-light responsive phototropism. These blue-light responses require various classes of photo-receptors, one of which is the blue-light responsive phototropins (consisting of phot1 and phot2)

Structurally, both phototropins are made up of both a photo-sensory domain (consisting of both a LOV1 and a LOV2 domain at the N-Terminus) and an output domain (consisting of a serine/threonine kinase domain at the C-Terminus)

Figure 1: (A) Diagram showing the structure of the blue light receptive phototropin. (B) Diagram showing the structure of the LOV2 domain with bound FMN co-factor. (Image by Dr John Christie, University of Glasgow)

Aside from being a member of the phototropin family, both LOV domains belong to a larger receptor family known as the PAS receptors due to their association with co-factor binding. They act by binding a flavin mono-nucleotide (FMN) in order to form a covalent adduct with a conserved cysteine residue. In darkness, FMN binds non-covalently, and upon irradiation with light or around 476nm, this binds covalently, and shows an emission spectra of 510-550nm, and giving off green fluorescence. The reaction can be regarded as a reversible photo-cycle, and the bound FMN co-factor is what causes fluorescence.

Within the photo-sensory domain, the most important domain is the LOV2 domain as this has been shown play a significant role in blue-light induced responses, and therefore we have engineered the LOV2 domain as a reporter. (Cho et al 2007)

The small size of LOV2 (~300 bp) and it's ability to be used under anoxic conditions are benefits of using it as a reporter, whereas classical reporters such as GFP are much larger (~700 bp) and lack this ability. The ability to work under anoxic conditions makes this reporter ideal work work in biofilms. LOV2 has also been shown to be coupled to many domains, for example phosphodiesterase or kinases.

There is a variant of LOV2 which shows better fluorescence and recovery from photo-bleaching, making it an optimised version of LOV2 for use as a reporter. This is known as iLOV, and this is also available on the registry (https://parts.igem.org/Part:BBa_K660004)

Usage and Biology

Sequence and Features

Assembly Compatibility:

• 10
  INCOMPATIBLE WITH RFC[10]

  Illegal PstI site found at 312
  
• 12
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• 21
  INCOMPATIBLE WITH RFC[21]

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• 23
  INCOMPATIBLE WITH RFC[23]

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• 25
  INCOMPATIBLE WITH RFC[25]

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  Illegal AgeI site found at 287
  
• 1000
  INCOMPATIBLE WITH RFC[1000]

  Illegal SapI.rc site found at 32