Light-activated histidine kinases in three bacteria-Pseudomonas syringae (plant pathogen), Brucella species (animal pathogens), and Erythrobactor litoralis (marine bacterium) utilize a LOV domain

SWARTZ TE; FREDERICKSON MA; PARIS G; DIEGO JOSE COMERCI; RAJASHEKARA G; KIM JG; MUDGETT MB; UGALDE, R. A.; GOLDBAUM, F. A.; BRIGGS, W. R.

Chicago, Illinois

Congreso; Botany and Plant Biology 2007. Joint Congress; 2007

Plant phototropins utilize a FMN-binding chromophore module designated LOV domain in sensing blue light signals inducing phototropism and other blue-light responses. Irradiation of purified LOV domains leads to the formation of an adduct between the C(4a) carbon of the FMN and a neighboring cysteine leading to a protein conformational change and activation of autophosphorylation and signal transduction. Putative LOV domains coupled to histidine kinases (LOV-HK) have now been identified by sequence homology in a large number of bacteria (Aba Losi, personal communication). Purified LOV-HKs from P. syringae, B. melitensis and E. litoralis undergo light-activated cysteinyl adduct formation via a flavin triplet and subsequent autophosphorylation, likely on a histidine. The adduct decays over minutes for the E. litoralis and P. syringae enzymes but not that from B. melitensis. Biochemical memory of the light pulse in inducing phosphorylation depends on the presence of adduct. In Brucella abortus, infectivity of macrophages kept in the light is about ten-fold greater compared to a mutant lacking the enzyme. In the dark wild-type infectivity is similar to that of the mutant, supporting a role for light in intracellular B. abortus replication. The role of the LOV-HKs in the other two bacteria is currently unknown. We propose that the LOV-HKs represent a new and wide-spread class of bacterial photoreceptors.