Coordination and redox state–dependent structural changes of the heme-based oxygen sensor AfGcHK associated with intraprotein signal transduction
| Autor: | Veronika Fojtikova, Michal Rosůlek, Petr Man, Martin Stranava, Toru Shimizu, Marketa Martinkova, Petr Kolenko, Jan Dohnálek, Tereza Skálová, Václav Martínek, Alzbeta Lengalova, Jan Bláha |
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| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
030102 biochemistry & molecular biology Chemistry Stereochemistry Autophosphorylation Histidine kinase Cell Biology Biochemistry 03 medical and health sciences chemistry.chemical_compound 030104 developmental biology Protein kinase domain Helix Hydrogen–deuterium exchange Globin Signal transduction Molecular Biology Heme |
| Zdroj: | Journal of Biological Chemistry. 292:20921-20935 |
| ISSN: | 0021-9258 |
| Popis: | The heme-based oxygen sensor histidine kinase AfGcHK is part of a two-component signal transduction system in bacteria. O2 binding to the Fe(II) heme complex of its N-terminal globin domain strongly stimulates autophosphorylation at His183 in its C-terminal kinase domain. The 6-coordinate heme Fe(III)-OH− and -CN− complexes of AfGcHK are also active, but the 5-coordinate heme Fe(II) complex and the heme-free apo-form are inactive. Here, we determined the crystal structures of the isolated dimeric globin domains of the active Fe(III)-CN− and inactive 5-coordinate Fe(II) forms, revealing striking structural differences on the heme-proximal side of the globin domain. Using hydrogen/deuterium exchange coupled with mass spectrometry to characterize the conformations of the active and inactive forms of full-length AfGcHK in solution, we investigated the intramolecular signal transduction mechanisms. Major differences between the active and inactive forms were observed on the heme-proximal side (helix H5), at the dimerization interface (helices H6 and H7 and loop L7) of the globin domain and in the ATP-binding site (helices H9 and H11) of the kinase domain. Moreover, separation of the sensor and kinase domains, which deactivates catalysis, increased the solvent exposure of the globin domain-dimerization interface (helix H6) as well as the flexibility and solvent exposure of helix H11. Together, these results suggest that structural changes at the heme-proximal side, the globin domain-dimerization interface, and the ATP-binding site are important in the signal transduction mechanism of AfGcHK. We conclude that AfGcHK functions as an ensemble of molecules sampling at least two conformational states. |
| Databáze: | OpenAIRE |
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