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	Cho, H.-Y., Tseng, T.S., Kaiserli, E., Sullivan, J., Christie, J.M. and Briggs, W.R. (2007) Physiological roles of the light, oxygen, or voltage domains of phototropin 1 and phototropin 2 in Arabidopsis1. Plant Physiology, 143 (1). pp. 517-529. ISSN 0032-0889		Cho, H.-Y., Tseng, T.S., Kaiserli, E., Sullivan, J., Christie, J.M. and Briggs, W.R. (2007) Physiological roles of the light, oxygen, or voltage domains of phototropin 1 and phototropin 2 in Arabidopsis1. Plant Physiology, 143 (1). pp. 517-529. ISSN 0032-0889
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-	[[File:Ilovephotobleaching.JPG]]	+	[[File:Ilovephotobleaching.JPG]] Figure 4: Image demonstrating photobleaching reversibility of iLOV: Left – iLOV pre-bleach, Centre – iLOV post-bleach, and Right – iLOV post-recovery. Image taken from Chapman et al (2008) The photoreversible fluorescent protein iLOV outperforms GFP as a reporter of plant virus infection. PNAS, 105 (50) pp. 20038 - 20043

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Revision as of 19:34, 20 September 2011

Lov 2 Domain

Fluorescent proteins have transformed our ability to visualise, quantify and monitor expression of proteins and other molecules within cells. One of the more commonly used fluorescent proteins is GFP (Green Fluorescent Protein) Plants contain a vast array of different photoreceptors which allow them to detect light around them in order to induce responses. One class of such receptors is the phototropins (phot1 and phot2). These are blue-light responsive domains which allow responses such as phototropism (the unidirectional movement of plants in response to blue light). Phototropins are structurally made up of two regions: a photosensory domain (N-Terminus) and a serine/threonine kinase domain (C-Terminus). The photosensory region consists of two LOV domains (Light, oxygen and voltage domain) known as LOV1 and LOV2 which are each ~110 amino acids long. These domains are a subgroup of the larger receptor group known as the PAS family, because they are associated with co-factor binding. Each of the two LOV domains acts by binding a flavin mononucleotide (FMN) in order to form a covalent adduct with a conserved cysteine residue. The photosensory region consists of two LOV domains (Light, oxygen and voltage domain) known as LOV1 and LOV2 which are each ~110 amino acids long. These domains are a subgroup of the larger receptor group known as the PAS family, because they are associated with co-factor binding. Each of the two LOV domains acts by binding a flavin mononucleotide (FMN) in order to form a covalent adduct with a conserved cysteine residue. Research was carried out to investigate the roles played by both LOV domains in phototropism, and it was found that LOV 2 of both phot1 and phot2 plays a significant role, whereas LOV on only plays a role in phot1 (Cho et al 2007) LOV domain activity can be monitored by fluorescence. In darkenss, FMN binds non-covalently, and upon irradiation with light, this binds covalently. The reaction can be regarded as a reversible photocycle. This bound FMN co-factor is what gives the green fluorescence

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) Figure 2: Diagram showing phototropism (unidirectional bending) of an oat seedling in response to blue light. (Image by Dr John Christie, University of Glasgow)

iLOV Over time, LOV varients have been isolated, some of which show better fluorescence and photostability than classic LOV2. One of these has been named iLOV, and in studies whereby it has been used in comparison to GFP to track plant infections, it has outperformed GFP. GFP is around 700bp long, whereas iLOV is much smaller at around 300 bp. For this reason it is thoughtto be better suited as a reporter for the movement of things such as viruses. Unlike GFP which photobleaches irreversibly, iLOV undergoes spontaneous recovery from photobleaching under high intensity exposure to UV. This photobleaching reversibility is due to the changing state between the fluorescent and non-fluorescent form of the bound FMN chromopore.
Figure 3: Digram showing movement of TMV (tobacco mosaic virus. On the left shows TMV with iLOV, and the centre and right show TMV with GFP. We can see that TMViLOV shows systemic infection, whereas TMVGFP shows poor, or no infection.Image taken from: Chapman, S. et al (2008) The photoreversible fluorescent protein iLOV outperforms GFP as a reporter of plant virus infection. PNAS, 105 (50) pp. 20038 - 20043

Biobrick Information

References

Chapman, S. et al (2008) The photoreversible fluorescent protein iLOV outperforms GFP as a reporter of plant virus infection. PNAS, 105 (50) pp. 20038 - 20043 Cho, H.-Y., Tseng, T.S., Kaiserli, E., Sullivan, J., Christie, J.M. and Briggs, W.R. (2007) Physiological roles of the light, oxygen, or voltage domains of phototropin 1 and phototropin 2 in Arabidopsis1. Plant Physiology, 143 (1). pp. 517-529. ISSN 0032-0889 Figure 4: Image demonstrating photobleaching reversibility of iLOV: Left – iLOV pre-bleach, Centre – iLOV post-bleach, and Right – iLOV post-recovery. Image taken from Chapman et al (2008) The photoreversible fluorescent protein iLOV outperforms GFP as a reporter of plant virus infection. PNAS, 105 (50) pp. 20038 - 20043