Positive regulatory protein of pdu and cob operons (PubMed:8071226, PubMed:7559322, PubMed:9023178). Positively autoregulates its own expression (PubMed:7559322). Cofactor biosynthesis; adenosylcobalamin biosynthesis [regulation]. Polyol metabolism; 1,2-propanediol degradation [regulation]. Increases expression of the entire cob operon about 90-fold irrespective of the growth medium; expression retains its sensitivity to vitamin B12 repression (PubMed:8071226). Cells lacking this gene are defective in aerobic and anaerobic degradation of propanediol (PubMed:9023178, PubMed:7559322).