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- Title
Effects of hydrogen sulfide on the heme coordination structure and catalytic activity of the globin-coupled oxygen sensor AfGcHK.
- Authors
Fojtikova, Veronika; Bartosova, Martina; Man, Petr; Stranava, Martin; Shimizu, Toru; Martinkova, Marketa
- Abstract
AfGcHK is a globin-coupled histidine kinase that is one component of a two-component signal transduction system. The catalytic activity of this heme-based oxygen sensor is due to its C-terminal kinase domain and is strongly stimulated by the binding of O or CO to the heme Fe(II) complex in the N-terminal oxygen sensing domain. Hydrogen sulfide (HS) is an important gaseous signaling molecule and can serve as a heme axial ligand, but its interactions with heme-based oxygen sensors have not been studied as extensively as those of O, CO, and NO. To address this knowledge gap, we investigated the effects of HS binding on the heme coordination structure and catalytic activity of wild-type AfGcHK and mutants in which residues at the putative O-binding site (Tyr45) or the heme distal side (Leu68) were substituted. Adding NaS to the initial OH-bound 6-coordinate Fe(III) low-spin complexes transformed them into SH-bound 6-coordinate Fe(III) low-spin complexes. The Leu68 mutants also formed a small proportion of verdoheme under these conditions. Conversely, when the heme-based oxygen sensor EcDOS was treated with NaS, the initially formed Fe(III)-SH heme complex was quickly converted into Fe(II) and Fe(II)-O complexes. Interestingly, the autophosphorylation activity of the heme Fe(III)-SH complex was not significantly different from the maximal enzyme activity of AfGcHK (containing the heme Fe(III)-OH complex), whereas in the case of EcDOS the changes in coordination caused by NaS treatment led to remarkable increases in catalytic activity.
- Subjects
HYDROGEN-deuterium exchange; REFRIGERANTS; HEMOGLOBINS; NONCARBOXYLIC acids; POISONOUS gases
- Publication
BioMetals, 2016, Vol 29, Issue 4, p715
- ISSN
0966-0844
- Publication type
Article
- DOI
10.1007/s10534-016-9947-z