Single tryptophanyl substitutions affect the structure of apomyoglobin
I Sirangelo1, S Tavassi, G Irace
1Dipartimento di Biochimica e Biofisica, Seconda Università di Napoli.
Mammalian myoglobins have two key tryptophanyl residues. Mutating these residues revealed their crucial role in globin folding and protein structure stability.
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Structure
Background:
- Mammalian myoglobins possess two conserved tryptophanyl residues (W7 and W14) in the N-terminal A helix.
- These residues are invariant, suggesting a significant functional role in myoglobin structure and stability.
Purpose of the Study:
- To investigate the specific contribution of W7 and W14 tryptophanyl residues to myoglobin structure and stability.
- To elucidate the role of these residues in protein folding and overall structural integrity.
Main Methods:
- Site-directed mutagenesis was employed to generate recombinant myoglobin variants with single tryptophanyl residues (W7 or W14).
- Mutant proteins were expressed in Escherichia coli and characterized using biophysical techniques, including far-ultraviolet circular dichroism and Soret absorption spectroscopy.
- Prosthetic group removal experiments were conducted to assess the impact on helical content.
Main Results:
- Mutant myoglobins with single tryptophanyl residues (W7 or W14) were correctly folded, exhibiting comparable far-ultraviolet circular dichroism and Soret absorption to wild-type myoglobin.
- The removal of the prosthetic group from mutant proteins resulted in a significantly greater loss of helical content compared to wild-type myoglobin.
- These findings indicate differential stability contributions from W7 and W14.
Conclusions:
- Tryptophanyl residues W7 and W14 play a critical role in maintaining the structural integrity and stability of myoglobin.
- These residues are essential for proper globin folding and contribute significantly to the overall stability of the myoglobin structure, particularly after prosthetic group removal.
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