A SAXS STUDY OF THE LIGHT-SENSING REACTION OF PLANT AND BACTERIAL PHYTOCHROMES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Protein photoreceptors allow biological organisms to sense, process and transmit the information contained in ambient light. Are light intensities sufficient to support growth? What time of day / year is it? Is a neighboring organism blocking access to sunlight? Plants and bacteria use photoreceptors from the phytochrome family to find the answer to all of these questions. We want to understand the molecular mechanism underlying phytochromes¿¿ biological function. Phytochromes are large, water-soluble multi-domain photoreceptors. Light activation of phytochromes has been shown to induce large-scale conformational changes. The protein fold for most phytochrome domains is known, thus allowing us to built molecular model of these domains by homology modeling. The goal of the proposed research is to use Small Angle X-ray scattering data to assemble the molecular models of individual domains into a model for the full-length phytochrome. In addition we would want to determine how this domain arrangement changes as a result of light-activation.