Curated Optogenetic Publication Database

Abstract: Light control over enzyme function represents a novel and exciting field of biocatalysis research. Blue-light photoreceptors of the Light, Oxygen, Voltage (LOV) family have recently been investigated for their applicability as photoactive switches. We discuss here the primary photochemical events leading to light activation of LOV domains as well as the proposed signal propagation mechanism to the respective effector domain. Furthermore, we describe the construction of LOV fusions to different effector domains, namely a dihydrofolate reductase from Escherichia coli and a lipase from Bacillus subtilis. Both fusion partners retained functionality, and alteration of enzyme activity by light was also demonstrated. Hence, it appears that fusion of LOV photoreceptors to functional enzyme target sites via appropriate linker structures may represent a straightforward strategy to design light controllable biocatalysts.

Abstract: Signal transduction proteins are organized into sensor (input) domains that perceive a signal and, in response, regulate the biological activity of effector (output) domains. We reprogrammed the input signal specificity of a normally oxygen-sensitive, light-inert histidine kinase by replacing its chemosensor domain by a light-oxygen-voltage photosensor domain. Illumination of the resultant fusion kinase YF1 reduced net kinase activity by approximately 1000-fold in vitro. YF1 also controls gene expression in a light-dependent manner in vivo. Signals are transmitted from the light-oxygen-voltage sensor domain to the histidine kinase domain via a 40 degrees -60 degrees rotational movement within an alpha-helical coiled-coil linker; light is acting as a rotary switch. These signaling principles are broadly applicable to domains linked by alpha-helices and to chemo- and photosensors. Conserved sequence motifs guide the rational design of light-regulated variants of histidine kinases and other proteins.

Abstract: The spectroscopic identification of sensory rhodopsin I by Bogomolni and Spudich in 1982 provided a molecular link between the light environment and phototaxis in Halobacterium salinarum, and thus laid the foundation for the study of signal transducing photosensors in prokaryotes. In recent years, a number of new prokaryotic photosensory receptors have been discovered across a broad range of taxa, including dozens in chemotrophic species. Among these photoreceptors are new classes of rhodopsins, BLUF-domain proteins, bacteriophytochromes, cryptochromes, and LOV-family photosensors. Genetic and biochemical analyses of these receptors have demonstrated that they can regulate processes ranging from photosynthetic pigment biosynthesis to virulence.

Abstract: The photosensor YtvA binds flavin mononucleotide and regulates the general stress reaction in Bacillus subtilis in response to blue light illumination. It belongs to the family of light-oxygen-voltage (LOV) proteins that were first described in plant phototropins and form a subgroup of the Per-Arnt-Sim (PAS) superfamily. Here, we report the three-dimensional structure of the LOV domain of YtvA in its dark and light states. The protein assumes the global fold common to all PAS domains and dimerizes via a hydrophobic interface. Directly C-terminal to the core of the LOV domain, an alpha-helix extends into the solvent. Light absorption causes formation of a covalent bond between a conserved cysteine residue and atom C(4a) of the FMN ring, which triggers rearrangements throughout the LOV domain. Concomitantly, in the dark and light structures, the two subunits of the dimeric protein rotate relative to each other by 5 degrees . This small quaternary structural change is presumably a component of the mechanism by which the activity of YtvA is regulated in response to light. In terms of both structure and signaling mechanism, YtvA differs from plant phototropins and more closely resembles prokaryotic heme-binding PAS domains.

Abstract: Here we present evidence for a physiologically relevant light response mediated by the LOV domain-containing protein YtvA in the soil bacterium Bacillus subtilis. The loss and overproduction of YtvA abolish and enhance, respectively, the increase in sigma(B)-controlled ctc promoter activity at moderate light intensities. These effects were absent in the dark and in red light but present under blue-light illumination. Thus, activation of the general stress response in B. subtilis is modulated by blue light.

Abstract: For single-cell and multicellular systems to survive, they must accurately sense and respond to their cellular and extracellular environment. Light is a nearly ubiquitous environmental factor, and many species have evolved the capability to respond to this extracellular stimulus. Numerous photoreceptors underlie the activation of light-sensitive signal transduction cascades controlling these responses. Here, we review the properties of the light, oxygen, or voltage (LOV) family of blue-light photoreceptor domains, a subset of the Per-ARNT-Sim (PAS) superfamily. These flavin-binding domains, first identified in the higher-plant phototropins, are now shown to be present in plants, fungi, and bacteria. Notably, LOV domains are coupled to a wide array of other domains, including kinases, phosphodiesterases, F-box domains, STAS domains, and zinc fingers, which suggests that the absorption of blue light by LOV domains regulates the activity of these structurally and functionally diverse domains. LOV domains contain a conserved molecular volume extending from the flavin cofactor, which is the locus for light-driven structural change, to the molecular surface. We discuss the role of this conserved volume of structure in LOV-regulated processes.