The LOV domain from Brucella LOV-HK: The role of the C-terminal helical flanking region in the light-to-signal propagation (poster)

MARIANA GALLO; JIMENA RINALDI; MARTIN ARAN; SEBASTIÁN KLINKE; GASTÓN PARIS; DANIEL O. CICERO; FERNANDO A. GOLDBAUM

Frauenchiemsee

Congreso; 35th FGMR Discussion Meeting & Joint Conference of the German, Italian and Slovenian Magnetic Resonance Societies; 2013

German Magnetic Resonance Society

LOV domains are blue-light-activated signaling modules present in a wide range of sensory proteins. Light modulates the virulence of the bacteria Brucella abortus through a LOV-histidine kinase (LOV-HK). The Brucella LOV domain adopts the alpha/beta PAS domain fold and dimerizes through the hydrophobic beta-scaffold, which appears as a key element in the light activation [1]. According to secondary structure predictions, Brucella LOV-HK harbors a C-terminal helix (J-alpha) contiguous to the LOV core that is estimated to be 34 residues long with no sequence similarity to other known LOV proteins. To explore the functional importance of the J-alpha 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 (LOVJ-alpha). We found that LOVJ-alpha, as the LOV core, is dimeric in solution and slowly returns to the dark state after being illuminated. The J-alpha helix is shorter than predicted, followed by an unstructured region to the C-terminus. The J-alpha helix is flexible and exposed to solvent. Its conformation does not change upon illumination. These results suggest that the J-alpha helix in the LOVJ-alpha construct is not participating in the signal transduction, though the situation may be different in the full-length protein. The implications of these results in the context of others LOVJ-alpha proteins are discussed.