Isolation of a gene encoding nodulin-like intrinsic protein of Escherichia coli

Members of the membrane intrinsic protein (MIP) family are expressed in various organisms including plants, insects, and vertebrates. E. coli is known to have a MIP member gene, glycerol facilitator (G1pF). Here we report the isolation of E. coli gene encoding BniP, bacterial nodulin-like intrinsic protein. BniP encodes a 231 amino acid, 24 kDa protein with 42% amino acid identity to Nod26, 38% amino acid identity to AQP1, and 29% amino acid identity to G1pF. Analysis of deduced amino acid sequence predicted a hydrophobic protein with six membrane-spanning domains. Expression of BniP in Xenopus oocytes induced slight increase in osmotic water permeability, but not glycerol or ion permeability. Our results showed that BniP is a new member of the MIP channel-forming proteins of E. coli.