Figure 6.

The spatial arrangement of the core proteins in the central plaque. (A) The relative postitions of the N- and C-termini as proven in Supplementary Materials. The geometry is presented in the context of the spacing between the IL2 layer and the central plaque. The lines connecting the termini follow the color coding of the FRET categories in Figure 4. (B) The lattice pattern of Spc42 in the IL2 layer based on the two-dimensional projection map of protein density described in (Bullitt et al., 1997). The repeat units of 3- and sixfold symmetry are shown. (C–E) Steps in the construction of the model of the central plaque. (C) Face-on view of the hexagonal unit of the central plaque shown from the perspective of the IL2 layer. Spc42 coiled coils projecting from the IL2 layer are at the vertices. The 30 Å lateral cross section of the fluorescent proteins are shown as circles. Orange, blue, yellow, and red represent the fluorescent proteins centered on C:Spc29, N:Spc42, C:Cmd1, and C:Spc110, respectively. The triangular arrangement of the proteins in the plane of the central plaque in A was introduced and sixfold rotational symmetry was applied. The proteins were closely packed to minimize the dimensions of the hexagonal unit. (D) Positions of termini. (E) Placement of N:Spc29. N:Spc29 and C:Spc29 are equidistant to C:Cmd1. N:Spc29 lies outside of the area, colored blue, where protein ends are close enough to C:Spc42 to register FRET. (F–H) Expanded schematic models of the central plaque that connect ends and includes features described in text and Materials and Methods. (F) Spc29 and Spc42; (G) Spc110 and Cmd1; and (I) all the components of the central plaque.