Structural and mechanistic determinants of c-di-GMP signalling

Bis-(3'-5' -cyclic dimeric GMP (c-di-GMP) is a ubiquito us second messenger that regulates cell surface-associated traits in bacteria. Components of this regulatory network include GGDEF and EAL domain-containing proteins that det ermine the cellular concentrations of c-di-GMP by mediatin g its synthesis and degradation, respectively. Crystal str ucture analyses in combination with functional studies have revealed the catalytic mechanisms and regulatory princip les involved. Downstream, c-di-GMP is recognized by PilZ d omain-containing receptors that can undergo large-scale do main rearrangements on ligand binding. Here, we review rec ent data on the structure and functional properties of the protein families that are involved in c-di-GMP signalling and discuss the mechanistic implications.