IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Illuminating the stress: LOVHK is related to a general stress response system in Brucella abortus
Autor/es:
SYCZ GABRIELA; TSENG, T; FREDERICKSON MARCUS; CARRICA MARIELA; WINSLOW BRIGGS; ROBERTO BOGOMOLNI; GOLDBAUM FERNANDO; PARIS GASTON
Lugar:
Buenos Aires
Reunión:
Congreso; International Research Conference Brucellosis 2011; 2011
Resumen:
Bacteria have evolved a variety of mechanisms to detect and respond to environmental changes. One of the main mechanisms is the two component signalling system (TCS), which consists of a sensor histidine kinase (HK) and its cognate response regulator protein (RR). When the HK detects the appropriate stimulus it autophosphorylates in a conserved histidine residue and then transfers the phosphoryl group to a conserved aspartate in the receiver domain (REC) of the RR. This activates the output domain of the RR which can direct gene expression by directly binding to DNA, catalyse metabolic reactions or modify protein-protein interactions. In previous experiments we have characterized an HK protein in Brucella abortus 2308, LOVHK, which has three domains: a LOV N-terminal domain, followed by a PAS domain and finally an HK domain which belongs to the HWE family. The LOV domain has a FMN molecule non-covalently bound as cofactor, and when it is exposed to blue light initiates a self-contained photocycle. The light-activated LOV domain forms a covalent adduct between the FMN and a conserved Cys. This promotes the autophosphorylation of the HK domain, which initiates a signal transduction pathway that ends with an increment in Brucella virulence. Using two-hybrid assays and phosphotransfer experiments we have identified two possible RR as interacting partners for LOVHK: one RR only has a REC domain and the other RR also has an additional domain. Phosphotransfer assays suggest that the first RR could be functioning as a phosphate sink for LOVHK, while the second RR could be responsible of a specific response to light. The second RR has a 72% homology to an anti-anti sigma factor which is involved in the General Stress Response (GSR) characteristic of alfaproteobacteria. Light activation of the GSR system is under evaluation using quantitative PCR. We are also building in B. abortus the mutants of the genes involved in the GSR system in order to confirm if LOVHK signals this system in vivo. In conclusion, our results suggest that LOVHK activates a stress response system that could modify Brucella virulence.