IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Crystallographic studies on the protein LOV-histidine kinase from Brucella abortus
Autor/es:
SEBASTIAN KLINKE; JIMENA J. RINALDI; GABRIELA SYCZ; GASTON PARIS; FERNANDO A. GOLDBAUM
Lugar:
Buenos Aires
Reunión:
Congreso; XL Reunión Anual de la Sociedad Argentina de Biofísica; 2011
Resumen:
<!-- @page { margin: 2cm } P { margin-bottom: 0.21cm } --> LOV (Light, Oxygen, Voltage) are ubiquitous sensory domains. In bacteria, most of the LOV domain-containing proteins are associated with histidine kinase (HK) output domains involved in signal transduction. HKs are the first members of two-component systems, which are involved in environmental sensing in bacteria regulating gene expression, chemotaxis and virulence. LOV domains bind FMN as cofactor and undergo a photocycle upon illumination. Blue light absorption gives rise to a covalent adduct between the FMN ligand and a cysteine residue from the protein. In the darkness, the covalent adduct decays thermally to the basal state. Recent evidence suggests that this adduct is the signal state of LOV-HKs. A protein containing a LOV domain followed by a PAS and an HK domain has been recently identified in Brucella abortus, an intracellular pathogen that causes a worldwide zoonosis called brucellosis. This protein binds FMN and undergoes a photocycle but it does not decay upon incubation in the darkness. Infection of macrophage cells with a Brucella mutant lacking the LOV gene shows an attenuated phenotype suggesting that the LOV-HK protein is a virulence factor1. Macrophage infection with Brucella wild type cells grown in the dark also shows a decrease in the number of intracellular bacteria, confirming the effect of light in bacterial virulence. As part of this project we aim to solve the crystallographic structure of LOV-HK, which will allow us a better understanding of the signal transduction effect between the LOV and HK domains, giving clues about the light sensing mechanism of LOV proteins and the general activation of histidine kinases. Additionally, we aim to explain the virulence enhancement by light in Brucella. In this talk we will show our recent progress in the project, describing the LOV domain structure at 1.64 Å resolution in the dark and preliminary results on HK domain crystals. In addition, we will also illustrate our present strategies to cover as much as possible of the whole LOV-HK protein in single constructs.