Figure 3:

BMC shell proteins exhibit quaternary structure variations and several modes of flexibility. (a) Geometric renderings highlight variations that have been observed especially within the Permuted BMC protein type including: flat disks (purple), flat disks with beta-barrel protrusions (turquoise), twisted structures (chartreuse), six-fold screws (orange) and rearrangement to pentamers (magenta). (b) Proteins of the Permuted BMC-T⁽⁺⁾ type are often observed as stacked disks with variations in pore openness/occlusion. Stacked disks have been reported with two closed pores (deep blue), one open and one closed pore (slate) or two open pores (light blue).