INVESTIGADORES
CARRICA Mariela Del Carmen
congresos y reuniones científicas
Título:
NtrYX, a redox activated two-component system in Brucella: signal transduction and transcriptional networks
Autor/es:
FERNANDEZ IGNACIO; CARRICA MARIELA; GASTÓN PARIS; FERNANDO A. GOLDBAUM
Lugar:
Heidelberg
Reunión:
Congreso; EMBO EMBLSymposium: New Approaches and Concepts in Microbiology; 2013
Resumen:
Brucella is a genus of facultative intracellular bacteria
responsible for a zoonotic disease called Brucellosis. Given that its
replicative niche is a microaerobic environment, Brucella needs to sense oxygen
availability in order to generate an adaptive response. Our group has
identified an oxygen/redox
sensor called NtrY that is involved in the adaptation of
Brucella to microaerobiosis and is important for its ability to replicate in
macrophages.
NtrY is a membrane-bound histidine kinase with cytosolic
HAMP and PAS domains. In a recent article we demonstrated that NtrY binds heme
and the activity of the protein increases upon reduction of its cofactor. Our
current work allowed us to establish that the isolated PAS domain interacts
with heme (therefore it is the sensor domain) and performing
titration experiments we could obtain a Kd= 40μM for that binding process.
Previously we had shown that NtrY phosphorylates NtrX, its
cognate response regulator, which belongs to the NtrC-like response regulators
subfamily. Our recent experiments demonstrated that NtrX is a stable dimer in
solution able to form higher oligomers and binds ATP and ADP with
comparable affinity. Gel shift assays indicate that NtrX
binds to a promoter sequence within its operon. Using transcriptional fusions,
we could determine that NtrX autoregulates its expression, stimulating the
transcription from two different promoters.
We also published a connection between the PrrBA and NtrYX
systems, in which PrrA enhances the transcription of NtrYX. In order to
investigate possible links with other signaling cascades, we performed qRT-PCR
using an NtrYX mutant strain. This approach allowed us discover that PhoP
is upregulated when NtrY is absent, and that NtrBC is under
the control of NtrY. These findings represent the first steps into the
description of a transcriptional network that involves NtrYX signaling system
in the adaptation to microaerobiosis, a central aspect in the pathogenesis of
Brucella.