Curated Optogenetic Publication Database

Abstract: Light-oxygen-voltage (LOV) domain proteins represent a versatile class of photoreceptors capable of regulating a wide range of light-dependent biological functions. While a lot of studies have focused on the photochemistry of LOV domains, the mechanisms of signal generation and propagation in multidomain LOV proteins remain incompletely understood. Here, we investigated two multidomain proteins, using time-resolved infrared spectroscopy. The measurements resolve the entire photocycle dynamics from picoseconds to hours and uncover distinct patterns of local and global structural responses. The two multidomain proteins under study, YF1 and PAL, exhibit nearly identical dynamics during excitation and intersystem crossing on the nanosecond timescale, reflecting conserved local interactions between the chromophore and its highly conserved binding pocket. Multiscale simulations attribute minor spectral differences in this regime to a phenylalanine residue located near the chromophore present only in one of the two LOV domains. The similarities, however, end at the microsecond timescale, where adduct formation already involves global structural adaptations. By experimentally isolating the response of the histidine kinase effector domain in the synthetic photoreceptor YF1, we show that major structural adaptions of the effector domain occur concurrently with cysteine-adduct formation and that the Jα-helix putatively mediates unidirectional communication between domains. In PAL, light-induced opening of the RNA binding site during the adduct formation is additionally followed by a subsequent rearrangement in the distal PAS domain after 3 s. This highlights the pivotal yet distinct roles of the Jα-helix in signal transmission, which depend on the domain topology. Ultimately, our study not only deepens the current understanding of signal transduction in full-length LOV proteins, but also contributes to the fundamental framework for the future application of LOV domains in optogenetic engineering.

Abstract: Photoactive yellow protein (PYP) is one of the typical light sensor proteins. Although its photoreaction has been extensively studied, no downstream partner protein has been identified to date. In this study, the intermolecular interaction dynamics observed between PYP from Rhodobacter capsulatus (Rc-PYP) and a possible downstream protein, PYP-binding protein (PBP), were investigated. It was found that UV light induced a long-lived product (pUV*), which interacts with PBP to form a stable hetero-hexamer (Complex-2). The reaction scheme for this interaction was revealed using transient absorption and transient grating methods. Time-resolved diffusion detection showed that a hetero-trimer (Complex-1) is formed transiently, which produced Complex-2 via a second-order reaction. Any other intermediates, including those from pBL, do not interact with PBP. The reaction scheme and kinetics are determined. Interestingly, long-lived Complex-2 dissociates upon excitation with blue light. These results demonstrate that Rc-PYP is a photochromic and new type of UV sensor to sense the relative intensities of UV-A and blue light.

Abstract: Recently, re-purposing of cyanobacterial photoreceptors as optogentic actuators enabled light-regulated protein expression in different host systems. These new bi-stable optogenetic tools enable interesting new applications, but their light-driven working mechanism remains largely elusive on a molecular level. Here, we study the optogenetic cyanobacteriochrome Am1-c0023g2 with isotope labeling and two dimensional infrared (2D-IR) spectroscopy. Isotope labeling allows us to isolate two site-specific carbonyl marker modes from the overwhelming mid-IR signal of the peptide backbone vibrations. Unlike conventional difference-FTIR spectroscopy, 2D-IR is sensitive to homogeneous and inhomogeneous broadening mechanisms of these two vibrational probes in the different photostates of the protein. We analyse the 2D-IR line shapes in the context of available structural models and find that they reflect the hydrogen-bonding environment of these two marker groups.