IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Illuminating the stress: A light-activate transduction pathway activates a General Stress Response system in Brucella
Autor/es:
GASTON PARIS; GABRIELA SYCZ; FERNANDO A. GOLDBAUM
Lugar:
Galveston
Reunión:
Conferencia; Gordon Research Conference on Photosensory Receptors and Signal Transduction; 2012
Resumen:
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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 sigma-like 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 with
PhyR, an anti-anti sigma factor, which is involved in the General
Stress Response (GSR) characteristic of alphaproteobacteria. 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.