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:
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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.