Molecular insights into the photoactivation mechanism of the Brucella blue-light sensing histidine kinase (Póster)

WANDA M. VALSECCHI; MARÍA V. COSENTINO; ELIANA S. IBARRA; LISANDRO H. OTERO; ALEJANDRO CRISTÓFALO; FERNANDO A. GOLDBAUM; SEBASTIÁN KLINKE; JIMENA RINALDI

Rosario

Congreso; L Reunión Anual de la Sociedad Argentina de Biofísica (SAB); 2022

Sociedad Argentina de Biofísica (SAB)

In response to light, and as part of a two-component system, the Brucella abortus blue light-activated histidine kinase (LOV-HK) increases its autophosphorylation, modulating the virulence of this microorganism. The aim of our project is to study the signaling mechanism in this photoreceptor in order to understand how the detection of light in the LOV domain is coupled to the enzymatic performance of the HK domain. Based on the three‑dimensional structure of full-length LOV‑HK (wild‑type, WT) in the light state and partial structures in the dark state, we have proposed a light‑gated transition involving a marked increase of asymmetry from a slightly asymmetric straight inactive structure in the dark state to a highly asymmetric bent active conformation in the light state. We hypothesize that such a change involves a series of events that includes dimer rearrangement, coiled-coil rotary switch, and bending of helical connectors, leading ultimately to an enhancement in the flexibility of the HK domain. In order to test our hypothesis, we are interested in obtaining the three‑dimensional structure of full-length LOV‑HK WT in the dark state and its dark-adapted variant, C69S. Here, we characterize the oligomeric state of C69S by means of static light scattering and crosslinking. Besides, we include results on the light sensibility of both variants, and the efforts to obtain structural information by X-ray crystallography and cryo‑EM as alternative approaches.