text: 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 residue. LOV domains are e.g. encountered in phototropins, which are blue-light-sensitive protein complexes regulating a great diversity of biological processes in higher plants as well as in micro-algae.  Phototropins are composed of two LOV domains, each containing a non-covalently bound flavin mononucleotide (FMN) chromophore in its dark-state form, and a C-terminal Ser-Thr kinase.
  Upon blue-light absorption, a covalent bond between the FMN chromophore and an adjacent reactive cysteine residue of the apo-protein is formed in the LOV2 domain. This subsequently mediates the activation of the kinase, which induces a signal in the organism through phototropin autophosphorylation.
  While the photochemical reactivity of the LOV2 domain has been found to be essential for the activation of the kinase, the in vivo functionality of the LOV1 domain within the protein complex still remains unclear.