Synthesis of biologically active proteins as L6KD‐SUMO fusions forming inclusion bodies in Escherichia coli

Abstract

A new platform has been developed to facilitate the production of biologically active proteins and peptides in Escherichia coli. The platform includes an N‐terminal self‐associating L6KD peptide fused to the SUMO protein (small ubiquitin‐like protein modifier) from the yeast Saccharomyces cerevisiae, which is known for its chaperone activity. The target proteins are fused at the C termini of the L6KD‐SUMO fusions, and the resulting three‐component fusion proteins are synthesized and self‐assembled in E. coli into so‐called active inclusion bodies (AIBs). In vivo, the L6KD‐SUMO platform facilitates the correct folding of the target proteins and directs them into AIBs, greatly simplifying their purification. In vitro, the platform facilitates the effective separation of AIBs by centrifugation and subsequent target protein release using SUMO‐specific protease. The properties of the AIBs were determined using five proteins with different sizes, folding efficiencies, quaternary structure, and disulfide modifications. Electron microscopy shows that AIBs are synthesized in the form of complex fibrillar structures resembling “loofah sponges” with unusually thick filaments. The obtained results indicate that the new platform has promising features and could be developed to facilitate the synthesis and purification of target proteins and protein complexes without the use of renaturation.