The EAL domain is an around 250-amino acid signaling domain. It is made of four conserved regions and has been named EAL according to a conserved sequence within the second of these regions. The EAL domain is found in a large number of eubacterial multi-domain proteins involved in signal transduction. The EAL domain is found in association with other domains of the prokaryotic two-component signal transduction systems, such as the GGDEF domain (see <PDOC50887>), the response regulatory domain (see <PDOC50110>), the PAS repeat and the PAC domain (see <PDOC50112>), the MHYT domain, the HAMP domain (see <PDOC50885>), the GAF domain, the TPR repeat, or the FHA domain (see <PDOC50006>). It has been proposed that the EAL domain might function as a diguanylate phosphodiesterase. Accordingly, it contains several conserved acidic residues that could participate in metal binding and potentially might form a phosphodiesterase active site [1,2,3].

Some proteins known to contain an EAL domain are listed below:

• Acetobacter xylinum diguanylate cyclase (DGC).
• Acetobacter xylinum phosphodiesterase A (gene pdeA).
• Bacillus subtilis hypothetical protein ykoW.
• Bordetella pertussis bvgR protein.
• Escherichia coli rtn protein. It is involved in resistance to phages N4 and lambda.
• Escherichia coli hypothetical protein yahA.
• Escherichia coli hypothetical protein yciR.
• Escherichia coli hypothetical protein yddU.
• Escherichia coli hypothetical protein yfeA.
• Escherichia coli protein yhjK.
• Escherichia coli hypothetical protein yjcC.
• Klebsiella pneumoniae fimK protein.
• Mycobacterium tuberculosis hypothetical protein Rv1354c.
• Rhizobium sp. strain NGR234 hypothetical protein Y4LL.
• Synechocystis sp. strain PCC 6803 nitrogen fixation positive activator protein.
• Synechocystis sp. strain PCC 6803 hypothetical protein slr0359.

The profile we developed covers the entire EAL domain.