N-terminal-methionylated interleukin-1 beta has reduced receptor-binding affinity

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Interleukin-1 beta (IL-1β) is a key cytokine in inflammation.
• Recombinant protein production can lead to variations in N-terminal sequences.
• Understanding these variations is crucial for protein function and therapeutic applications.

Purpose of the Study:

• To investigate the impact of N-terminal methionine on interleukin-1 beta receptor binding affinity.
• To determine if structural differences account for altered binding.
• To elucidate the mechanism by which N-terminal modifications affect IL-1β function.

Main Methods:

• Recombinant protein expression and purification.
• Nuclear Magnetic Resonance (NMR) spectroscopy for structural analysis.
• Receptor-binding affinity assays.

Main Results:

• Recombinant IL-1β with unprocessed N-terminal methionine (MAPV-) exhibited a 10-fold lower receptor-binding affinity compared to protein with the authentic N-terminal sequence (APV-).
• NMR spectroscopy revealed no significant or only minor conformational differences between the methionylated and non-methionylated forms.
• The reduced binding affinity is not explained by major structural alterations.

Conclusions:

• The presence of an additional N-terminal methionine residue significantly reduces IL-1β receptor-binding affinity.
• This suggests a subtle, direct or indirect, perturbation of the receptor-binding region caused by the N-terminal methionine.
• The findings highlight the importance of precise N-terminal processing for maintaining the biological activity of recombinant IL-1β.