The effector protein ExoY secreted by Pseudomonas aeruginosa is a nucleotidyl cyclase with preference for GTP

Background Pseudomonas aeruginosa is an important opportunistic pathogen causing serious pulmonary, urogenital and systemic infections. P. aeruginosa injects four effector proteins into host cells via the type III secretion system. ExoY is one of these proteins. ExoY was originally classified as adenylyl cyclase with homology to the typical calmodulin-stimulated adenylyl cyclase exotoxins CyaA from Bordetella pertussis and edema factor from Bacillus anthracis, but the pathophysiologial function of ExoY has remained elusive [1,2]. Recently, our group showed that CyaA and edema factor possess a rather broad base specifity (ATP >> CTP > UTP) [3,4], raising the question of wether ExoY may also bind and metabolize nucleoside 5’triphosphates other than ATP. Methods We determined cyclic nucleotide concentrations in cells transfected with ExoY plasmid or infected with P. aeruginosa with a highly sensitive HPLC-MS/MS method. Moreover, we determined the catalytic activity of purified ExoY.