Purification and characterization of human recombinant interleukin-1 beta

Area of Science:

• Biochemistry
• Molecular Biology
• Immunology

Background:

• Interleukin-1 (IL-1) beta is a key cytokine involved in inflammatory and immune responses.
• Production of recombinant IL-1 beta is essential for studying its structure-function relationships and therapeutic potential.

Purpose of the Study:

• To clone and express the mature human interleukin-1 (IL-1) beta in Escherichia coli.
• To purify and characterize the recombinant IL-1 beta (rIL-1 beta).
• To assess the biological activity and structural properties of the purified rIL-1 beta.

Main Methods:

• Cloning of human IL-1 beta cDNA and expression in E. coli.
• Purification of the 17-kDa soluble protein fraction.
• Characterization using amino acid analysis, sequencing, SDS-PAGE, spectroscopy, and biological assays.
• Circular dichroism spectroscopy to determine secondary structure.

Main Results:

• A 17-kDa biologically active rIL-1 beta was purified to homogeneity with 40% yield.
• Specific biological activity was determined to be 4.6 X 10(8) units/mg in an IL-2 induction assay.
• NH2-terminal sequencing showed heterogeneity, with 70% starting at Ala and 30% at Pro.
• Cysteine residues were reactive to alkylation, indicating no disulfide bonds, and S-carboxamidomethyl-rIL-1 beta retained activity.
• Circular dichroism indicated an extensive beta sheet structure.

Conclusions:

• The successful expression and purification of biologically active rIL-1 beta provide a valuable tool for further research.
• The characterization confirms the integrity and functional activity of the recombinant protein.
• Structural analysis suggests a predominantly beta sheet conformation, contributing to its biological function.