This domain is found in diverse bacterial signaling proteins. It is called EAL after its conserved residues. The EAL domain is a good candidate for a diguanylate phosphodiesterase function [1]. The domain contains many conserved acidic residues that could participate in metal binding and might form the phosphodiesterase active site [1].

1: Novel domains of the prokaryotic two-component signal transduction systems. Galperin MY, Nikolskaya AN, Koonin EV; FEMS Microbiol Lett 2001;203:11-21. PMID:11557134