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). Proteins such as this one with circularly permuted BMC domains may play a key role in conferring heterogeneity and flexibility in this BMC (Probable). 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 (PubMed:18786396). Interacts with PduV, probably via the beta-barrel which is predicted by modeling to be on the exterior of the BMC (PubMed:25646976). The N- and C-terminii are on the convex side of the hexamer, probably inside the BMC (PubMed:18786396) (Probable). Modeling suggests the beta-barrel is on the exterior of the BMC where it interacts with PduV (Probable). BMC production is induced by growth on 1,2-PD vitamin B12 medium. One side of the hexamer is concave which is lined by hydrophobic residues, the other side has a slightly protruding, 6-stranded beta-barrel which is occluded in PDB:3CGI by side chains. 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. 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 EutS/PduU family.