Blue light-activated histidine kinase: a novel two component system

GABRIELA SYCZ; GASTÓN PARIS; JIMENA RINALDI; HERNÁN BONOMI; SEBASTIÁN KLINKE; FERNANDO A. GOLDBAUM

Potrero de los Funes, San Luis

Congreso; XLVII Reunión Anual SAIB; 2011

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

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