The Escherichia coli phnB gene is found next to an operon of fourteen genes (phnC-to-phnP) related to the cleavage of carbon-phosphorus (C-P) bonds in unactivated alkylphosphonates, supporting bacterial growth on alkylphosphonates as the sole phosphorus source. It was originally considered part of that operon. PhnB appears to play no direct catalytic role in the usage of alkylphosphonate. Although many of the proteins in this family have been annotated as 3-demethylubiquinone-9 3-methyltransferase enzymes by automatic annotation programs, the experimental evidence for this assignment is lacking. In Escherichia coli, the gene coding 3-demethylubiquinone-9 3-methyltransferase enzyme is ubiG, which belongs to the AdoMet-MTase protein family. PhnB-like proteins adopt a structural fold similar to bleomycin resistance proteins, glyoxalase I, and type I extradiol dioxygenases.