The interdomain structural dynamics of the chloroplast signal recognition particle (cpSRP) proteins, cpSRP43 and cpSRP54 is studied by single molecule FRET, FCS, and ensemble fluorescence spectroscopy. These proteins are important  in targeting and transporting the light harvesting chlorophyll-binding proteins (LHCP) to the thylakoid membrane for photosynthesis. Several double Cys and single Cys mutants of cpSRP43 and cpSRP54 proteins are cloned, expressed, purified and then specifically labeled with fluorescent dyes. Single molecule FRET and FCS equilibrium binding results suggest that  fluorescence labeling at the mutated residues does not affect the cpSRP43-cpSRP54 interaction. Furthermore, we find that cpSRP43 proteins are very heterogeneous in structure and that cpSRP43 proteins undergo complex interdomain structural dynamics when interacting with cpSRP54 protein. These results will help us to better understand how plants incorporate photosynthetic proteins into their highly-efficient solar energy conversion system

Heterogeneity in the structure and dynamics of chloroplast targeting proteins studied with single molecule fluorescence

243rd National Meeting (2012)

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