'', generated using ChimeraX. Part of the LOV2 domain is hidden for clarity of the active site containing FMN. The dotted blue lines represent hydrogen bonds predicted as important in binding. In green are Cys426 and Arg427 residues which are crucial in photoactivity and FMN binding, respectively, with mutations resulting in total loss of function of the protein. Upon photoexcitation, the sulfur (yellow) of Cys426 forms a covalent bond with the carbon 4 of FMN. (PDBe: 4EEP) Phototropins have two distinct light, oxygen, or voltage regulated domains (LOV1, LOV2) that each bind
flavin mononucleotide (FMN). There is also evidence to suggest that phototropins undergo
autophosphorylation at various sites across the enzyme. One study found that phototropins on the plasma membrane play a role in phototropism, leaf flattening, stomatal opening, and chloroplast movements, while phototropins on the chloroplasts only partially affected stomatal opening and chloroplast movement, suggesting that the location of the protein in the cell may also play a role in its signaling function. == References ==