Regulation of biofilm formation in Yersinia pestis

Plague biofilm development is controlled by positive (HmsT) and negative (HmsP) regulators. The GGDEF-domain protein HmsT appears to have diguanylate cyclase activity to synthesize bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP) from 2 GTP molecules. The EAL domain of HmsP has phosphodiesterase activity and likely degrades c-di-GMP. This second messenger molecule probably influences biofilm development by activating the glycosyl transferase activity of HmsR. Here we demonstrate the in vitro pH optimum for phosphodiesterase activity of HmsP and that an alanine substitution in residue L508, D626, or E686 within the EAL domain affects this enzymatic activity and the biological function of the protein. Finally, protein-protein interactions and the cytoplasmic location of the enzymatic domains of HmsT and HmsP are evaluated.