The LOV domain from Brucella LOV-histidine kinase: The role of the flanking regions.

RINALDI J, GALLO M, ARÁN M, KLINKE S, PARIS G, CICERO DO & GOLDBAUM FA.

Buenos Aires

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2013

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Light-oxygen-voltage (LOV) domains are blue-light signaling modules. They bind the cofactor FMN, which confers sensing function. Light modulates the virulence of the bacterium Brucella through a LOV-histidine kinase. The Brucella LOV domain adopts the alpha/beta PAS domain fold, consisting of a beta-sheet and helical connector elements. Our results point to the beta-scaffold as a key element in the light activation. This beta-sheet, on one side, 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 (J-helix) contiguous to the LOV core, which is estimated to be 37 residues long and a 25 residue-long N-terminal helix (N-helix), with no sequence similarity to other known LOV proteins. Solution experiments show that the N-helix is essential for the formation of a stable dimer. To explore the functional importance of the J-helix, we performed NMR studies with a construct consisting of the LOV core and the 37 C-terminal residues. The J-helix is 17 residuelong, flexible and exposed to the solvent. Val135, located at the Nterminus of the J-helix, changes its chemical environment upon illumination suggesting a pivotal role. These results are discussed in the context of the full-length protein.