Insect Secretory SUMOstar Expression Kit. A specific SUMOstar protease was engineered to specifically recognize and cleave the SUMOstar tag in vitro, liberating the protein-of-interest with a desired N-terminal amino acid (endogenous SUMO proteases do not cleave the SUMOstar fusion construct). Fusion proteins are targeted to the secretory pathway for folding and secretion. SUMOstar fusion enhances the expression level and solubility of fusion proteins in eukaryotic expression system. The SUMOstar tag protects the expression host from the cytotoxic effects of many protein fusion partners. The insect expression system offers an alternative to yeast expression systems, and often produces more functional protein through high-fidelity post-translational modifications and chaperone-mediated protein folding. Insect expression provides a cost effective eukaryotic alternative to mammalian expression systems for functional protein production.