Structural Insights into the HWE Histidine Kinase Family: The Brucella Blue Light-Activated Histidine Kinase Domain

J. RINALDI; M. ARRAR; G. SYCZ; M.L. CERRUTTI; P.M. BERGUER; G. PARIS; D.A. ESTRIN; M.A. MARTI; S. KLINKE; F.A. GOLDBAUM

JOURNAL OF MOLECULAR BIOLOGY

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2016 vol. 428 p. 1165 - 1179

0022-2836

In response to light, as part of a two-component system, the Brucella blue light-activated histidine kinase(LOV-HK) increases its autophosphorylation, modulating the virulence of this microorganism. The Brucellahistidine kinase (HK) domain belongs to the HWE family, for which there is no structural information. The HWEfamily is exclusively present in proteobacteria and usually coupled to a wide diversity of light sensor domains.This work reports the crystal structure of the Brucella HK domain, which presents two different dimericassemblies in the asymmetric unit: one similar to the already described canonical parallel homodimers (C) andthe other, an antiparallel non-canonical (NC) dimer, each with distinct relative subdomain orientations anddimerization interfaces. Contrary to these crystallographic structures and unlike other HKs, in solution, theBrucella HK domain is monomeric and still active, showing an astonishing instability of the dimeric interface.Despite this instability, using cross-linking experiments, we show that the C dimer is the functionally relevantspecies. Mutational analysis demonstrates that the autophosphorylation activity occurs in cis. The differentrelative subdomain orientations observed for the NC and C states highlight the large conformational flexibilityof the HK domain. Through the analysis of these alternative conformations by means of molecular dynamicssimulations, we also propose a catalytic mechanism for Brucella LOV-HK.