IIBBA   05544
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE BUENOS AIRES
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The LOV domain from Brucella LOV-histidine kinase: The role of the C- terminal helical flanking region in the light-to-signal propagation.
Autor/es:
MARIANA GALLO, JIMENA RINALDI, MARTÍN ARÁN, SEBASTIÁN KLINKE, GASTÓN PARIS, DANIEL O. CICERO, AND FERNANDO GOLDBAUM.
Lugar:
Frauenchiemsee
Reunión:
Congreso; 35th FGMR Discussion Meeting and Joint Conference of the German, Italian and Slovenian Magnetic Resonance Societies Advanced Magnetic Resonance, Methods and Applications; 2013
Institución organizadora:
Italian and Slovenian Magnetic Resonance Societies Advanced Magnetic Resonance
Resumen:
Light-oxygen-voltage (LOV) domains are blue-light-activated signaling modules present in a wide range of sensory proteins. They are defined as a subset of the larger PER-ARNT-SIM (PAS) superfamily that specifically binds a flavin cofactor, which confers blue-light-sensing function. Light modulates the virulence of the pathogenic bacterium Brucella abortus through a LOV-histidine kinase (LOV-HK) [1]. The Brucella LOV domain adopts the a/b PAS domain fold, consisting of a five-stranded antiparallel b-sheet and helical connector elements. The domain dimerizes through the hydrophobic b-scaffold in an antiparallel way. Our results point to the b-scaffold as a key element in the light activation [2]. This b-sheet is a chromophore/protein environment interface. On one side, it interacts with the FMN molecule and on the other side communicates with N- or C-terminal helical regions flanking the LOV core or directly with effector domains. According to secondary structure predictions, Brucella LOV-HK harbors a C-terminal helix (Ja) contiguous to the LOV core, which is estimated to be 34 residues long with no sequence similarity to other known LOV proteins. It is predicted to be a coiled coil. To explore the functional importance of the Ja helix and to gain insight into the Brucella LOV-HK light activation mechanism, we performed structural studies with a stable construct consisting of the LOV core and the 37 C-terminal residues (LOVJa). We found that LOVJa is also dimeric in solution and, as the LOV core, it slowly returns to the dark state after being illuminated. The Ja helix is shorter than predicted (17 residue-long), flexible and exposed to solvent. Its conformation does not change upon illumination. These results suggest that the Ja helix in the LOVJa construct is not participating in the signal transduction mechanism, yet the situation may be different for the full-length protein. The implications of these results in the context of other LOVJa proteins are discussed.