A minor shell protein of the bacterial microcompartment (BMC) dedicated to 1,2-propanediol (1,2-PD) degradation. The isolated BMC shell component protein ratio for J:A:B':B:K:T:U is approximately 15:10:7:6:1:1:2 (PubMed:12923081). Not required for structural integrity of BMCs nor to mitigate propionaldehyde toxicity, may selectively transport specific metabolites (PubMed:21239588). May be involved in electron transport across the BMC shell (Probable). Can be engineered to alter permeability of the BMC shell (PubMed:31674899). 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. Probably bound by a single Cys residue from each subunit; which protein provides the fourth ligand is unknown. Polyol metabolism; 1,2-propanediol degradation. Homotrimerizes to form a pseudohexamer; in wild-type the central triangular pore is probably blocked by the [4Fe-4S] center (PubMed:20870711, PubMed:22654060). Interacts with PduS (By similarity). BMC production is induced by growth on 1,2-PD vitamin B12 medium. No visible effect on BMC morphology. Slight growth impairment on 1,2-propanediol and vitamin B12. Artificial BMCs can be made in E.coli by expressing pduA-pduB/B'-pduT-pduU-pduN-pduJ-pduK (in this order). Enzymes can be targeted to the BMC, and appear to be encapsulated within it. When mutated at 9 positions (construct O3-33 with these mutations; K15A, M67L, N148A, N149L, E156S, E160A, K161Y, R167A, V169L) self-assembles into bodies with 24 subunits, suitable for nanotechnology uses. Removal of the [4Fe-4S] center by mutagenesis and different substitutions of Cys-38 allows an increased growth rate under certain limiting-conditions ('L-40' in PduA, pduQ deletion), strongly suggesting this subunit has acquired the ability to transport 1,2-PD, propionaldehyde and NAD(+)/NADH across the BMC shell. Bacterial microcompartments (BMC) 100-200 nm in cross section are formed during aerobic growth on minimal 1,2-PD-B12 or anaerobic growth on 1,2-PD-tetrathionate medium, but not during aerobic growth on glucose, anerobic growth on glucose or pyruvate-tetrathionate (PubMed:10498708). BMCs can constitute up to 10% of total cell protein (PubMed:12923081). Belongs to the bacterial microcompartments protein family.