A minor shell protein of the bacterial microcompartment (BMC) dedicated to 1,2-propanediol (1,2-PD) degradation. Overexpression of this protein leads to cells with either deposits or having lamina-like structures in the cytoplasm (PubMed:18332146). Not absolutely required to make artificial BMCs (PubMed:20417607). May selectively transport specific metabolites (By similarity). 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. 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. Seems to be bound by a single Cys residue from each of 4 subunits (Probable). 3 ligands are provided by each trimer, the fourth ligand could potentially bind another protein (Probable). The cluster is accessible from both sides of the trimer (PubMed:21245529). E(0) is +99 mV. Polyol metabolism; 1,2-propanediol degradation. Homotrimerizes to form a pseudohexamer with a large central pore, which is probably the binding site for the [4Fe-4S] center (PubMed:21245529). Interacts with PduS (PubMed:21103360). Originally suggested to be a homotetramer; this is incorrect (Probable). 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. Belongs to the bacterial microcompartments protein family.