A minor shell protein of the bacterial microcompartment (BMC) dedicated to 1,2-propanediol (1,2-PD) degradation. May selectively transport specific metabolites (By similarity). Not absolutely required to make artificial BMCs (PubMed:20417607). Proteins such as this one with circularly permuted BMC domains may play a key role in conferring heterogeneity and flexibility in this BMC (Probable). Expression of a cosmid containing the full 21-gene pdu operon in E.coli allows E.coli to grow on 1,2-propanediol (1,2-PD) with the appearance of bacterial microcompartments (BMC) in its cytoplasm. Overexpression of this protein leads to multiple smaller structures which appear to clump together in the cytoplasm. The 1,2-PD-specific bacterial microcompartment (BMC) concentrates low levels of 1,2-PD catabolic enzymes, concentrates volatile reaction intermediates thus enhancing pathway flux and keeps the level of toxic, mutagenic propionaldehyde low. Polyol metabolism; 1,2-propanediol degradation. Homohexamer with a central pore lined by a beta-barrel. Hexamers pack into a loose array. Interacts with PduV, probably via the beta-barrel, which is predicted by modeling to be on the exterior of the BMC (By similarity). Interacts with shell protein PduA (PubMed:20417607). One side of the hexamer is concave which is lined by hydrophobic residues, the other side has a slightly protruding, 6-stranded beta-barrel. Artificial BMCs can be made in E.coli by expressing pduA-pduB/B'-pduJ-pduK-pduN-pduU-pduT (in this order); pduT and pduU are optional, while pduA, pduB/B', pduJ, pduK and pduN are essential. A construct with the reversed gene order does not make BMCs (PubMed:20417607). Ethanogenic BMCs can be made in E.coli by targeting pyruvate decarboxylase (pdc) and alcohol dehydrogenase (adh) to them. PduP(1-18)-Pdc and PduD(1-18)-Adh strains targeted to the BMC (PduA, PduB, PduJ, PduK, PduN, PduU) make significantly more ethanol than strains where Pdc and Adh are not targeted to the BMC (PubMed:24933391). Belongs to the EutS/PduU family.