CAREER: Structural dynamics and mechanisms of photoreceptor signaling

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Photoreceptors enable organisms to mediate a vast range of biological responses to light, including photosynthesis, cell and organelle motility, visual transduction and circadian rhythms. These important cellular mediators are implicated in biofilm formation and can alter the virulence of organisms. Photoreceptors are also the prototype for light driven devices. Elucidating the underlying mechanisms of operation of photoreceptors remain a key driver for the development of the field of optogenetics. In most cases, the absorption of light results in chemical and structural changes of the proteins involved that ultimately produce the biological output. Despite extensive studies, many of the details of how this signal is propagated are poorly understood. The objective of this project is to determine the underlying molecular mechanisms that couple light absorption to the activation of downstream biological processes in a specific class of photoreceptors. This work will generate the first time-resolved molecular description of the dynamic transition between states for the Blue Light Using Flavoprotein (BLUF) class of proteins and by providing structural tools that will enable more efficient and effective serial crystallography experiments. The educational objective of this project is to generate a hybrid research/educational structural proteomics pipeline, involving groups of undergraduates and high school students. This crowd-sourcing program will not only provide an opportunity for groups of students to conduct hands-on, 'real' research in a controlled setting, but will leverage the strength in numbers to address a challenging and fundamentally important research problem. The research and educational objectives will be integrated through their parallel use of X-ray crystallography and through graduate student involvement and oversight in both aspects of the proposed work.The research objective of this project is to determine the intrinsic molecular determinants and dynamic structural features that drive structural changes and signaling events in blue-light using FAD (BLUF) proteins. In particular, the molecular changes that drive signal transduction during the dark to light transition will be elucidated and the mechanism of photo-induced complexation of specific BLUF receptor proteins and complexes will be determined. These studies will integrate time-resolved spectroscopic methods with static and dynamic structural characterization to map the spatial and temporal changes that occur during photoreceptor activation. In addition, an acoustically-mediated serial crystallography approach will be developed and implemented. This approach will be used to generate molecular movies of the structural changes that occur during signal transduction in BLUF proteins and will be broadly applicable as a means to conduct efficient time-resolved structural studies on a broad range of samples at any X-ray source.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.