Related Experiment Videos
Haem disorder in modified myoglobins. Effect of reconstitution procedures
Abstract:
Apomyoglobin was reconstituted with deuterohaem derivatives under various conditions. The fraction of disordered component, which is characterized by a 180 degree rotation of the haem group, for the various preparations was determined by n.m.r. spectroscopy. By using the procedures described, it was shown that the fraction of disordered component is minimized if the reconstitution is carried out with high-spin ferric haem derivatives within an experimentally determined optimum pH range of 8-9.5. Use of low-spin derivatives in either the ferrous or ferric forms leads to substantial increases in the fraction of disordered form. Attempted removal of the disordered form by selective oxidation and chromatographic purification was not effective.
Insights
Reconstituting apomyoglobin with high-spin ferric haem derivatives within pH 8-9.5 minimizes the disordered component. Low-spin derivatives significantly increase this disordered form, which is difficult to remove.
Area of Science:
- Biochemistry
- Spectroscopy
- Protein chemistry
Background:
- Apomyoglobin reconstitution is crucial for studying haem protein structure-function relationships.
- The presence of a disordered component can affect protein function and stability.
Purpose of the Study:
- To investigate the optimal conditions for reconstituting apomyoglobin to minimize a disordered haem component.
- To understand the influence of haem derivative spin state and pH on reconstitution outcomes.
Main Methods:
- Apomyoglobin reconstitution with various deuterohaem derivatives.
- Nuclear magnetic resonance (n.m.r.) spectroscopy to quantify the disordered component.
- Varying pH and haem derivative spin states (high-spin ferric, low-spin ferrous/ferric).
Main Results:
- The fraction of the disordered component was minimized when using high-spin ferric haem derivatives.
- An optimal pH range of 8-9.5 was identified for minimizing the disordered form.
- Low-spin haem derivatives (ferrous or ferric) substantially increased the disordered component fraction.
Conclusions:
- Optimal reconstitution of apomyoglobin involves high-spin ferric haem derivatives within a specific pH range (8-9.5).
- The spin state of the haem derivative is a critical factor influencing the formation of the disordered component.
- Selective oxidation and chromatography were ineffective in removing the disordered form.