Figure 4. The W-shaped accessible region in the r–θ–φ space.

(a) The accessible region for tetrameric models, embedding the conformations of 23 actual PLH bundles. The r values of the plausible models are displayed according to the colour scale at the top. Each black dot represents an actual PLH bundle. (b) Corresponding results for pentamers. In a,b, all the black dots are within the respective W shapes (that is, each black dot is within a voxel defined by eight plausible models as vertices that are separated by the smallest increments in (r, θ, φ)). (c,d) The conformations of the actual tetrameric and pentameric PLH bundles displayed on the θ–φ plane. In each plot a yellow oval encircles two channels that are either not or only distantly related but have similar conformations for their PLH bundles.