This degenerate GGDEF domain is found at the C-terminus of PelD, a membrane-bound c-di-GMP-specific receptor. It contains an RXXD motif resembling the allosteric inhibition site found in diguanylate cyclases . In PelD this RXXD motif binds to dimeric c-di-GMP [1].

1: Structure of the cytoplasmic region of PelD, a degenerate diguanylate cyclase receptor that regulates exopolysaccharide production in Pseudomonas aeruginosa. Whitney JC, Colvin KM, Marmont LS, Robinson H, Parsek MR, Howell PL; J Biol Chem. 2012;287:23582-23593. PMID:22605337