A number of bacterial proteins, some of which are involved in a general secretion pathway (GSP) for the export of proteins (also called the type II pathway) [1,2], have been found to be evolutionary related. These proteins are listed below:

• The 'E' protein from the GSP operon of: Aeromonas (gene exeE); Erwinia (gene outE); Escherichia coli (gene yheG); Klebsiella pneumoniae (gene pulE); Pseudomonas aeruginosa (gene xcpR); Vibrio cholerae (gene epsE) and Xanthomonas campestris (gene xpsE).
• Agrobacterium tumefaciens Ti plasmid virB operon protein 11. This protein is required for the transfer of T-DNA to plants.
• Bacillus subtilis comG operon protein 1 which is required for the uptake of DNA by competent Bacillus subtilis cells.
• Aeromonas hydrophila tapB, involved in type IV pilus assembly.
• Pseudomonas protein pilB, which is essential for the formation of the pili.
• Pseudomonas aeruginosa protein twitching mobility protein pilT.
• Neisseria gonorrhoeae type IV pilus assembly protein pilF.
• Vibrio cholerae protein tcpT, which is involved in the biosynthesis of the tcp pilus.
• Escherichia coli protein hofB (hopB).
• Escherichia coli hypothetical protein ygcB.
• Escherichia coli hypothetical protein yggR.

These proteins have from 344 (pilT and virB11) to 568 (tapB) amino acids, they are probably cytoplasmically located and, on the basis of the presence of a conserved P-loop region (see <PDOC00017>), probably bind ATP. As a signature pattern we selected a region that overlaps the 'B' motif of ATP-binding proteins.