IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Light regulates virulence in Brucella abortus by a LOV-domain histidine kinase protein
Autor/es:
PARIS, GASTON; DIEGO J. COMERCI; TREVOR E. SWARTZ; ROBERTO A. BOGOMOLNI; RODOLFO A. UGALDE; FERNANDO A. GOLDBAUM
Lugar:
Bath, UK
Reunión:
Congreso; 12th Congress European Society for Photobiology.; 2007
Resumen:
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Brucella
abortus
is a facultative intracellular pathogen that causes brucellosis in
domestic animals and humans. Brucella
invades and replicates inside professional and non-professional
phagocytes. Two-component sensor/histidine kinase signaling proteins
are widely recognized as environmental sensors in bacteria. B.
abortus
contains a LOV-histidine kinase (LOV-HK) protein. LOV domains which
belong to the PAS domain superfamily, are the light sensory modules
in plant, fungi and algae photoreceptors. LOV domains bind a single
molecule of FMN and undergo a self-contained photocycle that is
dependent on the presence of a highly conserved cysteine residue.
Upon illumination the reactive cysteine forms a covalent bond between
the sulfur and C4a carbon of FMN. In addition to the LOV domain this
protein also has PAS and histidine kinase domains. In order to
investigate the in
vivo
function of the Brucella
LOV-HK a knocked-out null mutant was obtained. Cell infection assays
of J774A.1 macrophages showed that LOV-HK knockout strain has an
attenuated phenotype as compared with the wild type. A complemented
strain expressing the LOV-HK gene in the LOV-HK knockout genetic
background was able to rescue the phenotype, with the same
replication rate as the wild type. However, a LOV-HK C69A replacement
which cannot under go light induced formation of the covalent adduct
between the FMN and the reactive cysteine showed the same infection
profile that the LOV-HK knockout strain, indicating that formation of
covalent adduct is essential for its biological activity. To
determine if LOV-HK functions as photoreceptor during host-pathogen
interactions, the infection experiment was performed in light vs.
dark conditions. Strikingly, the number of wild type intracellular
bacteria recovered from the culture kept in the dark was roughly one
order of magnitude less than in the light-treated culture, moreover,
no difference between dark and light conditions was detected with the
LOV-HK knockout mutant. Activation of LOV-HK protein by light could
be part of an adaptive mechanism present in Brucella
that
senses its transition from outside the organism and prepares the
bacteria for effective infection of a new mammalian host.