LOV2

LOV2 is the second light-oxygen-voltage sensing domain (LOV domain) found in plant phototropins, notably Phototropin 1. In many plants, phototropin 1 contains two LOV domains, LOV1 and LOV2; the term LOV2 is commonly used to refer to the second domain, especially the AsLOV2 variant from Avena sativa that has been extensively studied and repurposed for optogenetics.

LOV domains bind flavin mononucleotide (FMN) as a chromophore. Upon blue light (~450 nm) exposure, a covalent cysteine–FMN adduct forms, triggering conformational changes including unwinding of the C-terminal Jα helix. This alters the interaction surface of the domain and, in engineered contexts, controls binding partners or domain activity. The dark recovery back to the ground state occurs thermally over seconds to minutes, depending on sequence and environment.

In biotechnology, LOV2-based tools enable light control of protein localization, interactions, and signaling. Prominent systems include iLID (light-induced dimerization with SspB), LOVTRAP (light-controlled binding using Zdk1 and LOV2), and related constructs used to regulate transcription, cytoskeletal dynamics, or membrane recruitment. Variants of LOV2 have been engineered with altered recovery kinetics, spectral properties, or binding affinities to suit different applications.

LOV2 is derived from the phototropin photoreceptor in plants, with AsLOV2 derived from oat (Avena sativa). It has been widely used since the late 2000s as a modular photosensor in synthetic biology, enabling rapid, non-invasive control of cellular processes with blue light.