This family consists of several Proteobacterial phosphonate metabolism protein (PhnI) sequences. Bacteria that use phosphonates as a phosphorus source must be able to break the stable carbon-phosphorus bond. In Escherichia coli phosphonates are broken down by a C-P lyase that has a broad substrate specificity. The genes for phosphonate uptake and degradation in E. coli are organised in an operon of 14 genes, named phnC to phnP. Three gene products (PhnC, PhnD and PhnE) comprise a binding protein-dependent phosphonate transporter, which also transports phosphate, phosphite, and certain phosphate esters such as phosphoserine; two gene products (PhnF and PhnO) may have a role in gene regulation; and nine gene products (PhnG, PhnH, PhnI, PhnJ, PhnK, PhnL, PhnM, PhnN, and PhnP) probably comprise a membrane-associated C-P lyase enzyme complex [1].

1: Molecular genetic studies of a 10.9-kb operon in Escherichia coli for phosphonate uptake and biodegradation. Wanner BL, Metcalf WW; FEMS Microbiol Lett 1992;79:133-139. PMID:1335942