CONICET | Buscador de Institutos y Recursos Humanos

Flavin containing LOV (light, oxygen, or voltage) domains are distributed in the three kingdoms of life (Eukarya, Archaea, and Bacteria). LOV domains function as light-sensory modules in plant and algal phototropins and in fungal blue-light receptors. In most cases, the LOV domain is the primary sensory module that conveys a signal to protein domains with known or putative functions as diverse as regulation of gene expression, regulation of protein catabolism, and activation of serine/threonine kinases in eukaryotes and histidine kinases in prokaryotes. Histidine kinases, used for environmental sensing by bacterial two-component systems, are involved in regulation of bacterial gene expression, chemotaxis, phototaxis, and virulence. We have discovered that the prokaryotes Brucellamelitensis, Brucellaabortus, Erythrobacterlitoralis and Pseudomonas syringae contain light-activated histidine kinases (LOV-HK) that bind a flavinchromophore and undergo photochemistry indicative of cysteinyl-flavin adduct formation. Infection of macrophages by B. abortus was stimulated by light in the wild type but was limited in photochemically inactive and null mutants of LOV-HK, indicating that the flavin-containing histidine kinase functions as a photoreceptor regulating B. abortus virulence. The B. abortus LOV-HK appears to function as a photoreceptor that is directly related to Brucella survival and replication within macrophages. We are studying the downstream signaling partners of the LOV-HK photosensor. Recently, we identified a response regulator that is specifically phosphorylated by light-activated LOV-HK. Although high-resolution structures are available for a number of histidine kinase domains, it is not known how signal information is communicated from the sensor domain to the kinase domain, and how autophosphorylation is initiated. We are also conducting structural studies of the Brucella LOV-HK in order to answer this question.