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. Author manuscript; available in PMC: 2012 Apr 1.
Published in final edited form as: Curr Opin Struct Biol. 2011 Apr;21(2):223–231. doi: 10.1016/j.sbi.2011.01.006

Table 1.

Known structures of shell proteins from bacterial microcompartments.

Protein Structure Properties
α-Carboxysome (e.g. Halothiobacillus neapolitanus)
CsoS1A Single-BMC domain hexamer Major shell component.
CsoS1C Single-BMC domain hexamer Major shell component.
CsoS1D Tandem-BMC domain (permuted) trimer Trimers stack to form a hexamer with D3 symmetry; open and closed conformations suggest gated transport.
CsoS4A/B Pentamer (non-BMC domain) Minor shell component; believed to form icosahedral vertices.
β-Carboxysome (e.g. Synechocystis PCC6803)
CcmK1 Single-BMC domain hexamer Major shell component.
CcmK2 Single-BMC domain hexamer Major shell component.
CcmK4 Single-BMC domain hexamer Minor shell component.
CcmL Pentamer (non-BMC domain) Minor shell component; believed to form icosahedral vertices.
Pdu Microcompartment (e.g. Salmonella enterica)
PduA Single-BMC domain hexamer Major shell component.
PduT Tandem-BMC domain trimer Pore likely involved in electron transport or Fe-S cluster transport.
PduU Single-BMC domain hexamer (permuted) Minor shell component; pore is blocked by 6-stranded β-barrel in crystal structure.
Eut Microcompartment (e.g. S. enterica & E. coli)
EutK Single-BMC domain fused to helix-turn-helix (HTH) domain HTH motif with positively charged surface suggests role in nucleic acid binding.
EutL Tandem-BMC domain trimer Pore observed in open and closed conformations; probable role in gated transport.
EutM Single-BMC domain hexamer Probable major shell component.
EutN Non-BMC domain hexamer Crystallizes as a hexamer despite homology to pentameric CcmL/CsoS4 family; role unclear.
EutS Single-BMC domain (permuted) hexamer Hexamer forms bent structure with C2 symmetry; possible role in edge formation within shell.
Other Microcompartments
EtuB Tandem-BMC domain (permuted) trimer Part of presumptive ethanol utilization microcompartment in Clostridium kluyveri.
PduT homolog Tandem-BMC domain trimer Part of microcompartment of uncharacterized function in Desulfitobacterium halfniense.