TABLE 3.

Putative genes involved in oxidation of phosphite and hypophosphite

Putative gene	Mol wt of predicted product	Proposed function	Closest homolog (probability)a	Signatureb
ptxA	29,630	Binding-protein-dependent phosphite transporter, ATPase component	Rhizobium meliloti PhoC, phosphate transporter subunit (9e − 50)	ABC family, 152–156
ptxB	31,262	Binding-protein-dependent phosphite transporter, binding protein component	Escherichia coli PhnD, phosphonate transporter subunit (8e − 13)
ptxC	29,376	Binding-protein-dependent phosphite transporter, inner membrane component	Escherichia coli PhnE, phosphonate transporter subunit (8e − 37)	Binding-protein-dependent transport system inner membrane component, 173–201
ptxD	36,391	Phosphite dehydrogenase	Escherichia coli putative 2-hydroxyacid dehydrogenase, o365 (5e − 38)	d-Isomer-specific 2-hydroxyacid dehydrogenase signature 3, 226–242
ptxE	Truncated	Transcriptional regulator for ptx operon	Methanococcus jannaschii transcriptional regulator homolog MJ0300 (2.1e − 11)	lysR family, 18–48
htxA	32,482	α-Ketoglutarate-dependent hypophosphite dioxygenase	Dactylosporangium sp. l-proline 4-hydroxylase (2e − 11)
htxB	32,702	Binding-protein-dependent hypophosphite transporter, binding protein component	Rhizobium meliloti PhoD, phosphate transporter subunit (8e − 14)
htxC	30,804	Binding-protein-dependent hypophosphite transporter, inner membrane component	Escherichia coli PhnE, phosphonate transporter subunit (3e − 39)
htxD	37,286	Binding-protein-dependent hypophosphite transporter, ATPase component	Escherichia coli PhnC, phosphonate transporter subunit (2e − 42)	ABC transporter family, 149–163
htxE	29,379	Binding-protein-dependent hypophosphite transporter, inner membrane component	Rhizobium meliloti PhoE, phosphate transporter subunit (6e − 25)
htxF	16,701	C-P lyase subunit	Rhizobium meliloti PhnG, putative C-P lyase subunit (0.023)
htxG	21,082	C-P lyase subunit	Escherichia coli PhnH, putative C-P lyase subunit (7e − 11)
htxH	40,300	C-P lyase subunit	Escherichia coli PhnI, putative C-P lyase subunit (3e − 67)
htxI	Truncated	C-P lyase subunit	Escherichia coli PhnJ, putative C-P lyase subunit (4e − 81)
orf117	12,663		Escherichia coli hypothetical protein o123 (2e − 22)
orf86		Site-specific recombinase	Lactobacillus helveticus putative site-specific recombinase (3e − 4)

^aClosest homologs were determined by Blast searches against the National Center for Biotechnology Information nonredundant protein database on 24 April 1998. The probability represents the smallest sum score of the closest homolog identified in these searches. 

^bSignature sequences are from the PROSITE database. The numbers indicate the position of the conserved signature sequence for the indicated protein family.