Ricerc@Sapienza

Nutrients such amino acids play key roles in shaping the metabolism of microorganisms in natural environments and in host¿pathogen interactions. Among nutrients, Arginine can be perceived by the opportunistic human pathogen Pseudomonas aeruginosa to control the second messenger 3¿-5¿cyclic diguanylic acid (c-di-GMP). This dinucleotide is involved in biofilm formation, a multicellular lifestyle which confers to the bacterium protection against antibiotics and unfavorable conditions.
The intracellular levels of c-di-GMP are controlled by the rate of its synthesis and degradation, regulated by diguanylate cyclases (GGDEF signature) and phosphodiesterase (EAL and HD-GYP signatures) respectively.
Our group recently found that RmcA (Redox regulator of c-di-GMP) in the Pseudomonas aeruginosa is able to respond to Arginine to control c-di-GMP levels (Paiardini et al., 2018).
RmcA is a multidomain membrane protein harbouring a Venus Fly Trap (VFT) domain devoted to periplasmic Arginine binding, a transmembrane helix and a cytoplasmic part displays 3 PAS and 1 LOV domains linked to GGDEF-EAL catalytic tandem, where the hydrolysis of c-di-GMP occurs (Mantoni et al., 2018).
The aim is to gain details on the mechanism of control of Arginine on c-di-GMP hydrolysis. Understanding this mechanism will be useful to promote biofilm dispersion, in which cells are more sensitive to antimicrobic compounds, to treat chronic infection with combined strategies.
We starting to investigate about the activity of the same truncated constructs on RmcA from P. aeruginosa and putida, in order to identify possible common structural determinants responsible for the transduction mechanism. Furthermore, the architecture of transducers such RmcA is too complex to be suitable for full-length studies, so we identified a prototype protein able to change c-di-GMP levels in response to Arginine, showing a minimal architecture i.e., VFT, transmembrane helix, catalytic domain(s) (Fig.1).