Probably forms vertices in the bacterial microcompartment (BMC) dedicated to ethanolamine degradation (Probable). It may be involved in transporting positively charged molecules into and out of the BMC (Probable). Amine and polyamine degradation; ethanolamine degradation. Has been crystallized as a homohexamer with an acidic central pore with a diameter of 26 Angstroms on one side and 14 Angstroms on the other (PubMed:17588214, PubMed:18292340). In solution has been shown to be a pentamer (PubMed:23456886). Belongs to the CcmL/EutN family. In strain MG1655 the eut operon is interrupted by the CPZ-55 prophage, encoding 9 genes situated between eutA and eutB, which are translated in the other direction. CPZ-55 may prevent expression of the eut operon in strain MG1655. Strain W3110 does not have this prophage element and should be able to express the operon.