N- and C-terminal flanking regions modulate light-induced signal transduction in the LOV2 domain of the blue light sensor phototropin 1 from Avena sativa.
Light sensing by photoreceptors controls phototropism, chloroplast movement, stomatal opening, and leaf expansion in plants. Understanding the molecular mechanism by which these processes are regulated requires a quantitative description of photoreceptor dynamics. We focus on a light-driven signal transduction mechanism in the LOV2 domain (LOV, light, oxygen, voltage) of the blue light photoreceptor phototropin 1 from Avena sativa (oat). High-resolution crystal structures of the dark and light states of an oat LOV2 construct including residues Leu404 through Leu546 (LOV2 (404-546)) have been determined at 105 and 293 K. In all four structures, LOV2 (404-546) exhibits the typical Per-ARNT-Sim (PAS) fold, flanked by an additional conserved N-terminal turn-helix-turn motif and a C-terminal flanking region containing an amphipathic Jalpha helix. These regions dock on the LOV2 core domain and bury several hydrophobic residues of the central beta-sheet of the core domain that would otherwise be exposed to solvent. Light structures of LOV2 (404-546) reveal that formation of the covalent bond between Cys450 and the C4a atom of the flavin mononucleotide (FMN) results in local rearrangement of the hydrogen-bonding network in the FMN binding pocket. These rearrangements are associated with disruption of the Asn414-Asp515 hydrogen bond on the surface of the protein and displacement of the N- and C-terminal flanking regions of LOV2 (404-546), both of which constitute a structural signal.
Halavaty
Andrei S
AS
Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA.
Moffat
Keith
K
D000595:Amino Acid Sequence; D018554:Avena / Q000737:chemistry; D056931:Cryptochromes; D018360:Crystallography, X-Ray; D003624:Darkness; D005420:Flavoproteins / Q000737:chemistry / Q000502:physiology*; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000502:physiology*; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology* / Q000528:radiation effects*
D056931:Cryptochromes; D005420:Flavoproteins; D045322:Photosynthetic Reaction Center Complex Proteins