A volume-rendered representation of the apoRyR1 (orange) and ryRyR1 (blue) structures with the highlighted conformational changes. The ryRyR1 reconstruction was mirrored in the right panel for a clear comparison to the aporRyR1. The left panel depicts the view down onto the receptor from the cytoplasm. The right panel depicts the section through the isosurface indicated by the dashed line, with red arrows indicating the conformational transition of the SR extensions (dark-orange and blue circles for apoRyR1 and ryRyR1, respectively). Red arrows indicate the conformational changes of the SR extentions. 