The chloroplast signal recognition particle (cpSRP) is responsible for transporting light harvesting chlorophyll-binding protein (LHCP) to the thylakoid membrane. To further our understanding of this evolutionary unique transport system, we performed a range of FRET studies on the protein-protein interactions in the cpSRP to probe static and dynamic structural properties of the proteins and provide new insights into the structure-dynamics-function relationship of the cpSRP.We designed, expressed, purified and labeled several single- and double-cysteine mutants of the SRP component multidomain proteins, cpSRP43 and cpSRP54, to probe each domain of the proteins. FRET efficiencies and binding constants for each labeled mutant are obtained and our results are consistent with a model where the cpSRP54 M domain wraps around the CD2 domain of the cpSRP43. Single molecule FRET experiments show that there is a great deal of structural heterogeneity in cpSRP43, particularly across the Ank4-CD3 region.

Studying protein-protein interactions in the chloroplast signal recognition particle by ensemble and single molecule FRET

245th National Meeting (2013)

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