1 research outputs found
Disruption of the dimerization interface of the sensing domain in the dimeric heme-based oxygen sensor AfGcHK abolishes bacterial signal transduction
The heme-based oxygen sensor protein AfGcHK is a globin-
coupled histidine kinase in the soil bacterium Anaeromyxobac-
ter sp. Fw109-5. Its C-terminal functional domain exhibits
autophosphorylation activity induced by oxygen binding to the
heme-Fe(II) complex located in the oxygen-sensing N-terminal
globin domain. A detailed understanding of the signal transduc-
tion mechanisms in heme-containing sensor proteins remains
elusive. Here, we investigated the role of the globin domain’s
dimerization interface in signal transduction in AfGcHK. We
present a crystal structure of a monomeric imidazole-bound
AfGcHK globin domain at 1.8 Å resolution, revealing that the
helices of the WT globin dimer are under tension and suggesting
that Tyr-15 plays a role in both this tension and the globin
domain’s dimerization. Biophysical experiments revealed that
whereas the isolated WT globin domain is dimeric in solution,
the Y15A and Y15G variants in which Tyr-15 is replaced with
Ala or Gly, respectively, are monomeric. Additionally, we found
that although the dimerization of the full-length protein is pre-
served via the kinase domain dimerization interface in all vari-
ants, full-length AfGcHK variants bearing the Y15A or Y15G
substitutions lack enzymatic activity. The combined structural
and biophysical results presented here indicate that Tyr-15
plays a key role in the dimerization of the globin domain of
AfGcHK and that globin domain dimerization is essential for
internal signal transduction and autophosphorylation in this protein. These findings provide critical insights into the signal
transduction mechanism of the histidine kinase AfGcHK from
Anaeromyxobacter