InterPro domain: IPR028973

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 [ 1 , 2 , 3 ]. PA2721, an uncharacterized protein from P. aeruginosa also belongs to this family [ 4 ].

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.

1. Molecular biology of carbon-phosphorus bond cleavage. Cloning and sequencing of the phn (psiD) genes involved in alkylphosphonate uptake and C-P lyase activity in Escherichia coli B. J. Biol. Chem. 265, 4461-71
2. Mapping and molecular cloning of the phn (psiD) locus for phosphonate utilization in Escherichia coli. J. Bacteriol. 172, 1186-96
3. Evidence for a fourteen-gene, phnC to phnP locus for phosphonate metabolism in Escherichia coli. Gene 129, 27-32
4. 1.6 A crystal structure of a PA2721 protein from pseudomonas aeruginosa--a potential drug-resistance protein. Proteins 63, 1102-5