Structure of a Light-Activated LOV Protein Dimer That Regulates Transcription

Abstract

Light oxygen or voltage (LOV) domains are widely represented signaling modules in bacteria, archea, protists, plants and fungi. The Neurospora crassa LOV protein VIVID (VVD) allows adaptation to constant or increasing light levels and proper entrainment of circadian rhythms. The crystal structure of the fully light-adapted VVD dimer reveals the mechanism by which light driven conformational change alters oligomeric state. Photo-induced formation of a cysteinyl-flavin adduct generates a new hydrogen bond network that releases the N-terminus from the protein core and restructures an acceptor pocket for its binding on the opposite subunit. Substitution of residues key to the monomer/dimer switch have profound effects on light adaptation in Neurospora. The VVD dimerization mechanism provides the molecular details for how a large family of photoreceptors converts light responses to alterations in protein interactions.

A Native Threonine Coordinates Ordered Water to Tune Light-Oxygen-Voltage (LOV) Domain Photocycle Kinetics and Osmotic Stress Signaling in Trichoderma reesei ENVOY

“…1, A and B). Such behavior suggests that the oxidation potential of the FMN cofactor may reside within physiologically relevant ranges as has been observed previously in LOV protein variants (18,34) and has recently been shown of being competent for signal transduction (35). Thus, ENV1 may employ the semiquinone in dark state signaling.…”

“…We conclude that the rate of oxidation proceeds ϳ10-fold faster than adduct decay pathways in ENV1. Similar mixtures of oxidized and reduced semiquinones were observed in slow cycling variants of N. crassa VVD, where the kinetics of adduct decay and oxidation seemed to occur on similar time scales (18,34).…”

“…Such conformational changes have been observed in other MD simulations and have been implicated as a possible signal transduction mechanism (39). However, crystal structures and MD simulations indicate that signal transduction may rather involve only rotation of Gln 204 to H-bond to the newly protonated HN5 (3,34,40). Interestingly, an examination of HN5-water and HN5-Gln distances reveals a single site of water near HN5 that is stabilized by local ordering of Thr 101 (Fig.…”

Functional and topological diversity of LOV domain photoreceptors

“…Although most structure-function studies on LOV proteins to date focus on flavin photocycling, the structurefunction of the linker region, which is arguably more critical for engineering high-performance chimeras, is more varied and less established. Most reported chimeras are constructed from one of three LOV proteins whose sensor-linker interactions have been described by structural NMR (AsLOV2) (6) or by crystallography (VIVID, YtvA) (56,58,79). Further establishing principles of how optical signals are transmitted between sensor and effector through the linker region enhances our ability to rationally engineer novel and improved protein-based tools.…”

Full-length structure of a monomeric histidine kinase reveals basis for sensory regulation

“…We conclude that, whereas V119A stabilizes the inhibited state, G102K and V115A destabilize it, resulting in high darkstate activity. Notably, residues Val115 and Val119 are located on the same Iβ-strand as Gln118, a conserved glutamine that changes its hydrogen bonding pattern with the flavin chromophore upon illumination (23)(24)(25), playing a key role in signaling (26,27). Propagation of light-induced structural changes in Gln118 along the Iβ strand could contribute to the drastic impairment of EL346 regulation when the Val115 and Val119 sidechains were truncated.…”