Aim: The aim of this study was thus to identify Lm proteins capable to bind cAMP.
Introduction: Infectious diseases are still a major cause of death worldwide. To infect a host and survive the environment, bacteria have to sense their surrounding and adjust their behaviour. In this adaptation process, cAMP (cyclic adenosine monophosphate) is known to be an important player in pathogens such as Pseudomonas spp., Vibrio spp. or Mycobacterium spp. The small molecule cAMP is a cyclic nucleotide that relays information from receptors to one or more effector proteins within a bacterial cell, functioning as a second messenger. To mediate a response, cAMP allosterically interacts with cAMP-binding proteins. Understanding how this happens is fundamental to predict how bacteria will adapt/act to/in a given context.
Methods: We recently showed that the human foodborne pathogen Listeria monocytogenes (Lm) produces cAMP. The aim of this study was thus to identify Lm proteins capable to bind cAMP. To do this, four candidate proteins selected by bioinformatics analyses were expressed, purified and studied biochemically. Three approaches were used: cAMP affinity chromatography; competitive cAMP affinity chromatography; and isothermal titration calometry (ITC).
Results: Among the four tested proteins, CbpA displayed cAMP-binding ability on the three approaches used.
Conclusion: Hence, our preliminary results showed that CbpA binds to cAMP. It is now mandatory to understand the relation between cAMP and CbpA, to determine the function of the protein itself and in complex with cAMP, and to understand the importance of this signalling system for virulence.