Fig. 4: Structure of the atomic model.

Each view contains an overview image with a zoomed inset of the highlighted area. The top row overview images contain the WT EM density surface maps with the wheat Hsp16.9 crystal structure (1GME) fitted in. The enlarged area images in the bottom row contain our pseudo-atomic model. A Focusing on one dimer in the 40mer environment. The surface model is based on the sharpened partial reconstruction of only the two top rings thresholded to better visualize the loops and the IEV-binding site (GSFSC resolution 6.1 Å). The pseudo-atomic model in the enlarged view at the bottom is color-coded as follows: All potential phosphorylation sites are colored magenta in the ball and stick representation. The ribbon of the central dimer is colored according to the color scheme in Fig. 1A. Thus, the MD is dark green, the ACD orange-red, and the CTR is blue. All other ribbons are colored gray. B Focus on one hexamer. Threshold of the surface map rendering was lowered to include the MD and NTS density. Color code as in A. The ribbons of all protein chains comprising one hexamer are colored as the central dimer in A, while the ribbons of other dimers are colored in gray. C Focus on the connectivities of one hexamer and the central core of the structure. The frontal density has been removed to reveal the inner structure. The threshold of the surface map rendering was lowered to include the MD and NTS density as in B. The blue C-terminal regions connect dimers at the outside of the oligomer, whereas the MD connects the dimers on the inside. Color-coding was performed as in A and the ribbon of the same hexamer is colored as in B. The volume containing middle domain and N-terminus has been highlighted in mint. Scale bar 10 nm. D WT 40mer reconstruction with all phosphorylation sites labeled with spheres that are part of the pseudo-atomic model. The sphere is centered around the Cβ atom of the respective residue. For clarity, the C-terminal phosphorylation sites are labeled red and the S144 in orange. The other two sites located toward the inside of the structure are labeled magenta. In the third image, the structure is cut open to show the inside that has been highlighted magenta to roughly indicate the volume encompassing over 60 phosphorylation sites.