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A steric mechanism for inhibition of CO binding to heme proteins
G S Kachalova1, A N Popov, H D Bartunik
1Max-Planck-Arbeitsgruppen für Strukturelle Molekularbiologie, Arbeitsgruppe Proteindynamik, Notkestrabetae 85, 22603 Hamburg, Germany.
Science (New York, N.Y.)
|April 16, 1999
Insights
Myoglobin
Area of Science:
- Biochemistry
- Structural Biology
- Biophysics
Background:
- Myoglobin is a protein that stores oxygen in muscles.
- Carbon monoxide is a toxic gas that can bind to myoglobin.
- Understanding how myoglobin binds ligands is important for various biological and medical applications.
Purpose of the Study:
- To elucidate the structural mechanisms of carbon monoxide binding to myoglobin.
- To understand how myoglobin reduces its affinity for carbon monoxide.
Main Methods:
- X-ray crystallography was used to determine the crystal structures of myoglobin.
- High-resolution (1.15 angstroms) structures were obtained for both deoxy- and carbon monoxide-ligated states.
- Analysis of structural changes upon ligand binding.
Main Results:
- Carbon monoxide binding to myoglobin at ambient temperatures requires coordinated movements of the heme, iron atom, and E and F helices.
- These movements relieve steric hindrance, facilitating ligand binding.
- This mechanism is crucial for modulating the heme group's affinity for carbon monoxide.
Conclusions:
- The study reveals the dynamic structural basis for carbon monoxide binding in myoglobin.
- Heme protein conformational changes play a key role in regulating ligand affinity.
- These findings provide insights into the interaction of heme proteins with toxic ligands.
Abstract:
The crystal structures of myoglobin in the deoxy- and carbon monoxide-ligated states at a resolution of 1.15 angstroms show that carbon monoxide binding at ambient temperatures requires concerted motions of the heme, the iron, and helices E and F for relief of steric inhibition. These steps constitute the main mechanism by which heme proteins lower the affinity of the heme group for the toxic ligand carbon monoxide.