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Abstract Insect-derived serine protease inhibitors (serpins) exhibit multiple inhibitory activities. Todate some functional roles for serpins in Hyphantria cunea Drury have been identified. Here, new functional features of the H. cunea serine protease inhibitor (dHC-serpin) were characterized. In this study, the cDNA encoding serpin was amplified from H. cunea (dHC) pupa fat body total RNA using RT-PCR. The full-length dHC-serpin cDNA encoded a protein of 440 amino acids with a predicted 19-amino acid signal peptide and a 421-amino acid functional domain. The functional domain was cloned into a pSUMO vector and transformed into Escherichia coli , resulting in the production of a pSUMO-dHC-serpin fusion protein. The soluble form of this protein was then purified by Ni-IDA chromatography. The SUMO-dHC-serpin fusion protein was then cleaved using a SUMO protease and purified again by Ni-IDA chromatography. dHC-serpin did not inhibit trypsin, elastase, proteinase K or cathepsin B, but strongly inhibited papain. The inhibitor retained its inhibitory activity over a broad range of pH (pH 2–12), temperature (20–50 °C), and DTT concentration (up to 100 mM). A complete loss of inhibitory activity was observed at pH 13 and 70 °C. Serpins generally serve as inhibitors that use a mobile reactive center loop (RCL) as bait to trap protease targets. dHC-serpin, like others serpins, binds papain using the RCL structure. Highlights • The full length dHC-serpin gene cloned from Hyphantria cunea Drury. • The SUMO-dHC-serpin fusion protein is highly soluble in Escherichia coli. • dHC-serpin exhibits activity against papain. • dHC-serpin remained active and stable between 20 °C and 50 °C and pH 2 and 12. • The reactive center loop region is important for dHC-serpin binding with papain. [ABSTRACT FROM AUTHOR]

A TRAIL-CM4 fusion protein in soluble form with tumor selective apoptosis and antibacterial functions was expressed in the Escherichia coli expression system and isolated through dialysis refolding and histidine-tag Nickel-affinity purification. Fresh Jurkat cells were treated with the TRAIL-CM4 fusion protein. Trypan blue staining and MTT analyses showed that, similar to a TRAIL positive control, Jurkat cell proliferation was significantly inhibited. Flow cytometry analyses using Annexin V-fluorescein revealed that Jurkat cells treated with the TRAIL-CM4 fusion protein exhibited increased apoptosis. Laser confocal microscopy showed that APB-CM4 and the fusion protein TRAIL-CM4 can bind to Jurkat cell membranes and initiate their destruction. ABP-CM4 enhances the antitumor activity of TRAIL by targeting and damaging the tumor cell membrane. In antibacterial experiments, agar well diffusion and bacterial growth inhibition curve assays revealed concentration-dependent TRAIL-CM4 antibacterial activity against Escherichia coli K12D31. The expressed TRAIL-CM4 fusion protein exhibited enhanced antitumor and antibacterial activities. Fusion protein expression allowed the two different proteins to function in combination. [ABSTRACT FROM AUTHOR]