1.S.2. The Bacterial Microcompartment Shell/Pore-forming Protein-2 (BMC-SP2) Family
In contrast to the BMC-SP1 family which consists of small proteins of about 100 aas, the BMC-SP2 family consists of proteins of somewhat greater than 200 aas and are non-homologous to the BMC-SP1 proteins. However, they contribute to shell formation, sometimes in the same BMC shell as a BMC-SP1 protein as in the ethanolamine utilizing (Eut) BMC of E. coli, and both types of shell proteins form pores (Takenoya et al. 2010). In contrast to EutL (BMC-SP1), the pore of EutM (BMC-SP2) appears to be positively carged, indicating specificity for different solutes. Moreover, only the pore of EutL can be triggered to open by exposure to zinc ions (Takenoya et al. 2010).