Modification of the Self-Aggregating Peptide L6KD to Produce Stable Active Inclusion Bodies in Escherichia coli

The synthesis of biologically active recombinant proteins and peptides in the form of active inclusion bodies (AIBs) significantly reduces production costs. Previously, we developed an original platform for the production of AIBs in Escherichia coli cells. It included the N-terminal self-aggregating peptide (SAP) L6KD fused to the SUMO (Smt3) protein of the yeast Saccharomyces cerevisiae, which is known for its chaperone activity. However, AIBs produced with this platform were sensitive to sonication and extrusion of cells with French press, leading to significant product loss during the cell lysate fractionation stage. To increase AIBs stability, we investigated modifications of the original SAP. we increased the hydrophobic core of SAPs and introduced additional intermolecular interactions between SAPs with disulfide or ionic bonds. The best results were obtained for peptides with an increased hydrophobic tail (L8KD), as well as for those containing sequences of 2‒4 cysteine residues directly at the N-terminus of the hydrophobic core of SAPs (C2L6KD, C3L6KD, C4L6KD). Integration of cysteine residues at a distance from the hydrophobic core of SAPs (C2G3L6KD, L6KDGSC2), as well as the formation of additional ionic bonds (KDL6KD, KDL8KD), did not lead to an increase in the stability of AIBs. The prposed SAP modifications did not significantly affect the synthesis of the target protein. Under sonication, the best-performing SAP variants increased AIB yield by 30‒40%. This improvement was also confirmed during cell disintegration by extrusion via French press.