Related Experiment Videos
Histidine-tailed microperoxidase-10: a pH-dependent ligand switch
1Department of Chemistry and Biochemistry, University of South Carolina, Columbia 29208, USA.
Biochemical and Biophysical Research Communications
|January 8, 1999
Summary
Ferric histidine-tailed microperoxidase-10 (His-MP10) undergoes a pH-dependent ligand switch. At low pH, it binds histidine and water, but switches to bis-histidine ligation at neutral and alkaline pH.
Area of Science:
- Biochemistry
- Biophysical Chemistry
Background:
- Microperoxidases are heme-containing peptides with biological relevance.
- Understanding the coordination chemistry of ferric heme proteins is crucial for elucidating their function.
Purpose of the Study:
- To investigate the pH-dependent changes in the axial ligation of ferric histidine-tailed microperoxidase-10 (His-MP10).
- To characterize the electronic and magnetic properties of His-MP10 across a wide pH range.
Main Methods:
- Electronic absorption spectroscopy.
- Magnetic circular dichroism (MCD) spectroscopy.
- Comparison with spectroscopic data of model heme compounds and myoglobin.
Main Results:
- Ferric His-MP10 exhibits two distinct species with a pKa of 4.4.
- Acidic ferric His-MP10 (pH 1.8) is ligated by histidine and water, similar to ferric mesoporphyrin-reconstituted myoglobin.
- Neutral and alkaline ferric His-MP10 (pH > 4.4) are bis-histidine ligated, with the C-terminal histidine acting as the sixth ligand.
Conclusions:
- Ferric His-MP10 demonstrates a pH-dependent axial ligand switch.
- The ligand switch involves a transition from histidine-water ligation at low pH to bis-histidine ligation at neutral and alkaline pH.
- This behavior differs from myoglobin and horseradish peroxidase, highlighting the unique coordination properties of His-MP10.