Integral to the protein structure/function paradigm, oligomeric state is typically conserved along with function across evolution. However, notable exceptions – such as the hemoglobins – show how evolution can enable new regulatory mechanisms by oligomerization changes. We examine this linkage in the histidine kinases (HKs), widely-distributed prokaryotic environmental sensors. While most HKs are transmembrane homodimers, our finding of a monomeric soluble HK (EL346, a photosensing Light-Oxygen-Voltage (LOV)-HK) raises questions about the relationship between oligomerization and regulation within this family. Here we characterize multiple EL346 homologs and find a diverse range of HK oligomeric states. Three LOV-HK homologs are dimers with differing structural responses to light, while two are Per-ARNT-Sim (PAS)-HKs that interconvert between differentially-active monomers and dimers, suggesting dimerization as a regulatory control. Finally, we examine putative interfaces in a dimeric LOV-HK, finding that multiple domains contribute to dimerization and function. Our findings suggest potential for novel regulation in this important family of environmental sensors.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)
- Immunology and Microbiology(all)
- Pharmacology, Toxicology and Pharmaceutics(all)