Structure of full-length FLS2 and BAK1 dimer complex by cryogenic electron microscopy

Name of applicant

Peter Klemmed Bjørk


DKK 820,000



Type of grant

Internationalisation Fellowships


Plants perceive a fragment of the bacterial flagellum as an indicator of bacterial invasion. The flagellum is a tail-like structure, which many bacteria depend upon for motility. The membrane-bound receptor protein FLS2 and the co-receptor BAK1 recognize the flagellum fragment and activation of the receptors initiates signal cascades ultimately leading to plant immunity. It is unknown how recognition of flg22 outside of the plant cell leads to immunity signaling inside the cell. Using cryogenic electron microscopy, I will determine the structure of full-length receptors FLS2 and BAK1. The protein structures will be used to elucidate the allosteric basis for transmembrane activation, which has previously been unknown.


Understanding how the structure of FLS2 and BAK1 facilitates trans-membrane activation will help us analyze why some plants show better immune responses towards bacterial flagellum. However, these receptors are just two of hundreds of this type of receptor in plants. This work will therefore serve as a starting point for structure determination and analysis of other receptors involved in immunity, development, or plant-microbe symbiosis. Ultimately, this information can guide breeders to produce crop varieties that are less dependent on pesticides, thus reducing yield loss, especially in countries with reduced access to pesticides.


FLS2 and BAK1 will be heterologously expressed in yeast cells. They will be purified and solubilized in detergent for easier handling. The pure protein fractions will then be frozen in the thinnest possible layer of ice on cryoEM grids optimized to obtain suitable particle distribution with a diversity of orientations. The protein complexes will be visualized using high-end Krios microscopes available at the NYU Langone Medical Center and data will be analyzed under the guidence of Professor David Stokes. David is an international expert in determining structures of membrane proteins and I plan to learn as much as possible from him during my stay in New York.

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