6otd
Globin sensor domain of AfGcHK in monomeric form, with imidazole
Structural highlights
FunctionGCHK_ANADF Member of the two-component regulatory system GcHK/Anae109_2439. Autophosphorylates in response to oxygen availability, and then transfers the phosphate group to a conserved Asp residue in the receiver domains of the cognate response regulator Anae109_2439, resulting in its activation.[1] Publication Abstract from PubMedThe heme-based oxygen sensor protein AfGcHK is a globin-coupled histidine kinase in the soil bacterium Anaeromyxobacter 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 transduction 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 A resolution, revealing that the helices of the wild-type 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 wild-type 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 preserved via the kinase domain dimerization interface in all variants, 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. Disruption of the dimerization interface of the sensing domain in the dimeric heme-based oxygen sensor AfGcHK abolishes bacterial signal transduction.,Skalova T, Lengalova A, Dohnalek J, Harlos K, Mihalcin P, Kolenko P, Stranava M, Blaha J, Shimizu T, Martinkova M J Biol Chem. 2019 Dec 30. pii: RA119.011574. doi: 10.1074/jbc.RA119.011574. PMID:31914416[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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