SAXS STUDY OF THE LIGHT SENSING REACTION OF PHYTOCHROME

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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. Phytochromes are photoreceptors found in plants and certain bacteria where they sense the duration and intensity of red and far-red light. According to the received light signals, phytochromes then control or modulate virtually every aspect of plant metabolism and development. Preliminary biochemical experiments suggest that light activation of phytochromes causes large inter-domain motions which are essential for signal transduction. To investigate the structural basis of this important signaling reaction, we will extend earlier static SAXS experiments by Tokutomi, et al. (FEBS 274, pp. 139-42 (1989). Using the higher resolution data obtainable at the superior SAXS facility at SSRL, we will be able to generate a more detailed, higher fidelity model of phytochrome. Additionally, we will investigate the role of domain rearrangements in the light-activated signaling reaction of phytochrome using time-resolved SAXS