Expression of the Recombinant Precursor and Putative Mature Forms of Human interleukin-37 isoform b (IL-37b) in E. coli Expression System

Abstract

Background and Objectives: IL-37b is a cytokine that may exist in several forms including a full-length precursor protein and its putative mature forms (IL-37b cleaved at E21, V46, and K53, respectively). In recent years, the role of IL-37b has been associated with the regulation of inflammation and inflammatory diseases. Previous studies focused on the intracellular activity of the cytokine, while the bioactivities of its variants when introduced in the extracellular environment has been limited and require further investigation. To enable this, the study produced precursor and truncated forms of IL-37b in an E. coli expression system.

Methodology: Recombinant proteins of the full-length (FL) and shorter forms (E21, V46, and K53) of IL-37b were produced in IPTG-induced E. coli BL21-CodonPlus(DE3)-RIPL strain and subsequently purified using Ni2+-NTA affinity, ion exchange, and size exclusion chromatography. The identity of the proteins was confirmed through western blotting and LC-MS.

Results: Findings show that the masses of the expressed proteins correspond to their respective theoretical masses with 24,134.75 0.04 Da for FL, 21,919.63 0.80 Da for E21, 19,298.57 0.04 Da for V46, and 18,551.21 0.04 Da for K53 at 90-95% purity. This confirms that the correct proteins have been produced and at high purity. Further, the tendency of FL to homodimerize was observed in this study, which may have implications in the extracellular processing and bioactivity of FL.

Conclusion: This study describes the successful expression and purification of recombinant precursor and putative mature forms of IL-37b in E. coli, which can be utilized for downstream characterization.