Curated Optogenetic Publication Database

Abstract: Photosensor proteins are important not only because of their biological functions but also because of their applications in optogenetics. To understand the molecular mechanism behind their biological functions and consequently seek possible applications to optogenetics, the dynamics of their intermolecular interaction (for example, association/dissociation reaction and conformational changes) upon photoexcitation need to be elucidated. Although it has been difficult to trace such reactions in the time domain using traditional spectroscopic techniques, the time-resolved diffusion method based on the transient grating technique has been demonstrated to possess a significant advantage in detecting such spectrally silent dynamics in a time-resolved manner. In this paper, the principle and studies on blue light sensor proteins, phototropins, are described. Reaction kinetics of dimerization, dissociation reactions, and conformational changes were measured, and reaction schemes were determined. This method can be employed to study protein reactions from the viewpoint of diffusion and to elucidate the reaction schemes and kinetics that cannot be detected by other spectroscopic methods.

Abstract: In this symposium, six speakers introduced the cutting-edge technologies and researches in optogenetics (Fig. 1). Optogenetics markedly revolutionized life science. This technique allows fast and precise control of a defined biological event, such as neuronal excitation, cell locomotion, gene expression, and so on, even in a complex system such as freely moving animals. Optogenetics has been realized through understanding the molecular properties of photoreceptors, developing new optical techniques, genetics in model systems, and modern brain science.

Abstract: Photoreceptor proteins have been used to study how protein conformational changes are induced by alterations in their environments and how their signals are transmitted to downstream factors to dictate physiological responses. These proteins are attractive models because their signal transduction aspects and structural changes can be precisely regulated in vivo and in vitro based on light intensity. Among the known photoreceptors, members of the blue light-using flavin (BLUF) protein family have been well characterized with regard to how they control various light-dependent physiological responses in several microorganisms. Herein, we summarize our current understanding of their photoactivation and signal-transduction mechanisms. For signal transduction, we review recent studies concerning how the BLUF protein, PixD, transmits a light-induced signal to its downstream factor, PixE, to modulate phototaxis of the cyanobacterium Synechocystis sp. PCC6803.

Abstract: First described about 15 years ago, BLUF (Blue Light Using Flavin) domains are light-triggered switches that control enzyme activity or gene expression in response to blue light, remaining activated for seconds or even minutes after stimulation. The conserved, ferredoxin-like fold holds a flavin chromophore that captures the light and somehow triggers downstream events. BLUF proteins are found in both prokaryotes and eukaryotes and have a variety of architectures and oligomeric forms, but the BLUF domain itself seems to have a well-preserved structure and mechanism that have been the focus of intense study for a number of years. Crystallographic and NMR structures of BLUF domains have been solved, but the conflicting models have led to considerable debate about the atomic details of photo-activation. Advanced spectroscopic and computational methods have been used to analyse the early events after photon absorption, but these too have led to widely differing conclusions. New structural models are improving our understanding of the details of the mechanism and may lead to novel tailor-made tools for optogenetics.