Dimer Asymmetry and Light Activation Mechanism in Brucella Blue-Light Sensor Histidine Kinase

Abstract

The ability to sense and respond to environmental cues is essential for adaptation and survival in living organisms. In bacteria, this process is accomplished by multidomain sensor histidine kinases that undergo autophosphorylation in response to specific stimuli, thereby triggering downstream signaling cascades. However, the molecular mechanism of allosteric activation is not fully understood in these important sensor proteins. Here, we report the full-length crystal structure of a blue light photoreceptor LOV histidine kinase (LOV-HK) involved in light-dependent virulence modulation in the pathogenic bacterium Brucella abortus. Joint analyses of dark and light structures determined in different signaling states have shown that LOV-HK transitions from a symmetric dark structure to a highly asymmetric light state. The initial local and subtle structural signal originated in the chromophore-binding LOV domain alters the dimer asymmetry via a coiled-coil rotary switch and helical bending in the helical spine. These amplified structural changes result in enhanced conformational flexibility and large-scale rearrangements that facilitate the phosphoryl transfer reaction in the HK domain. IMPORTANCE Bacteria employ two-component systems (TCSs) to sense and respond to changes in their surroundings. At the core of the TCS signaling pathway is the multidomain sensor histidine kinase, where the enzymatic activity of its output domain is allosterically controlled by the input signal perceived by the sensor domain. Here, we examine the structures and dynamics of a naturally occurring light-sensitive histidine kinase from the pathogen Brucella abortus in both its full-length and its truncated constructs. Direct comparisons between the structures captured in different signaling states have revealed concerted protein motions in an asymmetric dimer framework in response to light. Findings of this work provide mechanistic insights into modular sensory proteins that share a similar modular architecture.

Mining the Flavoproteome of Brucella ovis, the Brucellosis Causing Agent in Ovis aries

“…Other predicted virulent factors common in nearly all Brucella are the membrane bound sarcosine oxidase, the blue-light-activated histidine kinase, and the pyridoxamine 5′-phosphate oxidase family protein. The blue-light-activated histidine kinase increases its own autophosphorylation to modulate the microorganism virulence in B. abortus ( 72 , 96 , 97 ). The pyridoxamine 5′-phosphate oxidase family protein is very rare in other bacteria, but its conservation within Brucella suggests a particular still unclear function.…”

“…This group is completed with the predicted salicylate hydroxylase, the FAD:protein FMN transferase, the blue-light-activated histidine kinase, and the protein NrdI. Considering their above-mentioned envisaged roles for virulence upon infection in different bacteria (Table SP7), these four proteins might be also of particular relevance as drug targets ( 95 , 96 ).…”

Flaviolin-Like Gene Cluster Deletion Optimized the Butenyl-Spinosyn Biosynthesis Route in Saccharopolyspora pogona

“…The differential expression of these genes may be caused by the deletion of the type III polyketide synthase gene in clu13, which led to excessive accumulation of malonyl-CoA (Figure D). Moreover, we identified a series of significantly differentially expressed proteins and regulatory factors: PNPase have been reported to play potentially important roles in the butenyl-spinosyn biosynthesis; regulator Sp4674 (we named it Reg) belongs to the two-component system, which plays an important role in sensing and responding to changes in environmental cues; ,, XreR is a transcriptional regulator related to secondary metabolites. , The gene expression changes in S. pogona-Δclu13, as indicated by proteomic analyses, were complex and difficult to track; therefore, a gene function analysis was necessary to determine the key influencing factors of butenyl-spinosyn biosynthesis.…”

Membrane Sensor Histidine Kinases: Insights from Structural, Ligand and Inhibitor Studies of Full-Length Proteins and Signalling Domains for Antibiotic Discovery

“…With regard to SHK-specific inhibitors, there is also a paucity of knowledge on how agonists and antagonists bind to some target sites within SHK proteins; increased knowledge in this area would be beneficial for structure-based drug design strategies, which are currently less popular but nonetheless worthy of continued pursuance. Whilst the structures and functions of many individual SHK domains, domain hybrids and multi-domain SHKs are known, including natively soluble SHKs that lack transmembrane segments [ 67 , 68 , 69 , 70 , 71 , 72 ], all of which have contributed significantly to knowledge of these proteins, there remains a lack of structural data on full-length membrane SHKs which results in part from the technical challenges associated with their purification as intact active membrane proteins in sufficient milligram quantities for elucidation of their three-dimensional structures by crystallisation or other methods [ 73 ]. However, these challenges are being overcome and in this Review, we describe some of the emerging successes in the overexpression and purification of full-length active membrane SHKs, the methods used for their solubilisation and reconstitution using detergents, amphipols, liposomes, and nanodiscs, and some of the consequent successes in structural and ligand binding studies, thereby expanding upon and complementing other Reviews of SHKs to date, which have focused less on studies of full-length purified proteins.…”