Construction of a modified murine interferon alpha with increased stability

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Murine interferon alpha A (MuIFN-αA) is a crucial cytokine involved in immune responses.
• The role of specific amino acid residues, particularly cysteine, in protein stability and function is of significant interest.
• Understanding protein instability mechanisms is vital for developing more effective therapeutic proteins.

Purpose of the Study:

• To investigate the impact of substituting cysteine at position 86 with serine on the stability and activity of murine interferon alpha A.
• To determine if the free cysteine residue contributes to the inactivation and heat lability of MuIFN-αA.

Main Methods:

• Site-specific mutagenesis was employed to create the [Ser86] mutant of MuIFN-αA.
• Recombinant expression of the mutant protein was achieved in Escherichia coli using the lambda phage PL promoter.
• Inactivation kinetics and heat-induced denaturation/reactivation assays were performed to compare the mutant with the wild-type protein.

Main Results:

• The Ser86 mutant MuIFN-αA, lacking the free cysteine at position 86, exhibited slower inactivation compared to the wild-type protein.
• Heat-inactivated wild-type MuIFN-αA could not be reactivated.
• Heat-inactivated Ser86 mutant MuIFN-αA demonstrated significant reactivation (approximately 27.5%) in the presence of sodium dodecyl sulfate.

Conclusions:

• The free cysteine residue at position 86 in murine interferon alpha A is a key factor contributing to its instability.
• Substitution of this cysteine with serine enhances the protein's stability and allows for partial reactivation after heat denaturation.
• These findings have implications for protein engineering and the development of more stable interferon-based therapeutics.