A Light-oxygen-voltage-sensing domain (LOV domain) is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

sensor used by a large variety of higher plants, microalgae, fungi and bacteria to sense environmental conditions. In higher plants, they are used to control

phototropism In biology, phototropism is the growth of an organism in response to a light stimulus. Phototropism is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the ligh ...

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

relocation, and

stomata In botany, a stoma (: stomata, from Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the epidermis of leaves, stems, and other organs, that controls the rate of gas exchange between the internal air spa ...

l opening, whereas in fungal organisms, they are used for adjusting the

circadian A circadian rhythm (), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours. Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrai ...

temporal organization of the cells to the daily and seasonal periods. They are a subset of

PAS domain A Per-Arnt-Sim (PAS) domain is a protein domain found in all kingdoms of life. Generally, the PAS domain acts as a molecular sensor, whereby small molecules and other proteins associate via binding of the PAS domain. Due to this sensing capabilit ...

Chromophore

Common to all LOV proteins is the blue-light sensitive flavin chromophore, which in the signaling state is covalently linked to the protein core via an adjacent

cysteine Cysteine (; symbol Cys or C) is a semiessential proteinogenic amino acid with the chemical formula, formula . The thiol side chain in cysteine enables the formation of Disulfide, disulfide bonds, and often participates in enzymatic reactions as ...

residue. LOV domains are e.g. encountered in

phototropins Phototropins are blue light photoreceptor proteins (more specifically, flavoproteins) that mediate phototropism responses across many species of algae, fungi and higher plants. Phototropins can be found throughout the leaves of a plant. Along with ...

, which are blue-light-sensitive protein complexes regulating a great diversity of biological processes in higher plants as well as in micro-algae.

Phototropins Phototropins are blue light photoreceptor proteins (more specifically, flavoproteins) that mediate phototropism responses across many species of algae, fungi and higher plants. Phototropins can be found throughout the leaves of a plant. Along with ...

are composed of two LOV domains, each containing a non-covalently bound

flavin mononucleotide Flavin mononucleotide (FMN), or riboflavin-5′-phosphate, is a biomolecule produced from riboflavin (vitamin B2) by the enzyme riboflavin kinase and functions as the prosthetic group of various oxidoreductases, including NADH dehydrogenase, as ...

(FMN) chromophore in its dark-state form, and a C-terminal Ser-Thr

kinase In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule don ...

. Upon blue-light absorption, a covalent bond between the FMN chromophore and an adjacent reactive

residue of the apo-protein is formed in the LOV2 domain. This subsequently mediates the activation of the

, which induces a signal in the organism through phototropin

autophosphorylation Autophosphorylation is a type of post-translational modification of proteins. It is generally defined as the phosphorylation of the kinase by itself. In eukaryotes, this process occurs by the addition of a phosphate group to serine, threonine o ...

. While the photochemical reactivity of the LOV2 domain has been found to be essential for the activation of the

, the in vivo functionality of the LOV1 domain within the

complex still remains unclear.

Fungus

In case of the fungus ''

Neurospora crassa ''Neurospora crassa'' is a type of red bread mold of the phylum Ascomycota. The genus name, meaning 'nerve spore' in Greek, refers to the characteristic striations on the spores. The first published account of this fungus was from an infestatio ...

'', the

circadian clock A circadian clock, or circadian oscillator, also known as one’s internal alarm clock is a biochemical oscillator that cycles with a stable phase and is synchronized with solar time. Such a clock's ''in vivo'' period is necessarily almost exact ...

is controlled by two light-sensitive domains, known as the white-collar-complex (WCC) and the LOV domain vivid (VVD-LOV). WCC is primarily responsible for the light-induced

transcription Transcription refers to the process of converting sounds (voice, music etc.) into letters or musical notes, or producing a copy of something in another medium, including: Genetics * Transcription (biology), the copying of DNA into RNA, often th ...

on the control-gene frequency (FRQ) under day-light conditions, which drives the expression of VVD-LOV and governs the negative feedback loop onto the

. By contrast, the role of VVD-LOV is mainly modulatory and does not directly affect FRQ.

Natural and engineered functions of LOV domains

LOV domains have been found to control

gene expression Gene expression is the process (including its Regulation of gene expression, regulation) by which information from a gene is used in the synthesis of a functional gene product that enables it to produce end products, proteins or non-coding RNA, ...

through

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

binding and to be involved in redox-dependent regulation, like e.g. in the bacterium ''

Rhodobacter sphaeroides ''Rhodobacter sphaeroides'' is a kind of purple bacterium; a group of bacteria that can obtain energy through photosynthesis. Its best growth conditions are anaerobic phototrophy ( photoheterotrophic and photoautotrophic) and aerobic chemoh ...

''. Notably, LOV-based optogenetic tools have been gaining wide popularity in recent years to control a myriad of cellular events, including cell motility, subcellular organelle distribution, formation of membrane contact sites, microtubule dynamics, transcription, and protein degradation.

References

{{Protein domains Sensory receptors Signal transduction Molecular biology Plant physiology

Chromophore

Fungus

Natural and engineered functions of LOV domains

See also

References