A number of bacterial and archaebacterial proteins involved in transporting formate or nitrite have been shown [1] to be related:

• focA and focB, from Escherichia coli, transporters involved in the bidirectional transport of formate.
• fdhC, from Methanobacterium formicicum and thermoformicicum, a probable formate transporter.
• nirC, from Escherichia coli and Salmonella typhimurium, a probable nitrite transporter.
• Bacillus subtilis hypothetical protein yrhG.
• Bacillus subtilis hypothetical protein ywcJ (ipa-48R).

These transporters are proteins of about 280 residues and seem to contain six transmembrane regions. As signature patterns, we selected two conserved regions. The first one is located in what seems to be a cytoplasmic loop between the second and third transmembrane domains; the second is part of the fourth transmembrane region.

The 70 Kd yeast hypothetical protein YHL008c is highly similar, in its N-terminal section, to the prokaryotic members of this family.