(A) Cartoon representation of structures of the BMC shell proteins found in the HO shell, viewed from the side (top row) and from the top onto the concave side (bottom row; view point indicated by a blue arrow in the side view). One protein chain each is colored according to secondary structure (helix: red, sheet: yellow, first and last secondary structure elements colored darker) and marked N- and C-termini.
(B) Secondary structure diagrams of the shell proteins depicted in a. BMC-H consists of a single pfam00936 domain. HO-BMC-TS1 is a member of the BMC-TS-type that comprises a fusion of two pfam00936 domains. HO-BMC-TD2 and HO-BMC-TD3 are BMC-TD-type shell proteins that are a fusion of a permuted pfam00936 domain where β4 and α3 are located at the N-terminus. BMC-P contains the all-β-sheet pfam03319 domain.