Vesicle Nucleating peptide 6 (VNp6) mediates efficient soluble expression of recombinant proteins in Escherichia coli

Escherichia coli is a dominant host for recombinant protein production due to its well-characterized genetics and low cultivation cost, yet high-level intracellular expression frequently leads to insoluble inclusion bodies. Targeting proteins to the periplasm represents an effective strategy for improving soluble expression, but the efficiency of conventional signal peptides is highly protein-specific, restricting their universal utility. This study investigates an artificially engineered peptide, Vesicle Nucleating peptide 6 (VNp6), and systematically evaluates its capacity to mediate recombinant protein expression with green fluorescent protein (GFP) as a reporter. Results revealed that VNp6 markedly enhanced intracellular soluble GFP expression at 37 ℃, 25 ℃, and 16 ℃. Its intracellular fluorescence intensity was 128-fold and 220-fold higher than that of PelB and OmpA at 37 ℃, 82-fold and 113-fold at 25 ℃, and 107-fold and 160-fold at 16 ℃, respectively. Subcellular localization confirmed predominant periplasmic localization and improved solubility of the protein. Relative to the native periplasmic signal peptides FimH and PhoA, VNp6 improved solubility by 4‑fold and 14‑fold, respectively. For SacB, TVE, and amylase, solubility was enhanced by 27%, 30% and 17% at 16 ℃, respectively. Although extracellular protein accumulation was partially attributable to cell lysis, VNp6 consistently promoted periplasmic protein accumulation and enhanced soluble protein production across multiple recombinant proteins. Collectively, these results demonstrate that VNp6 serves as a powerful tool for improving periplasmic protein accumulation and soluble expression in E. coli expression systems.