In this study, Hespintor, a
protein with unknown function, was screened and obtained from the
hepatoblastoma cell line, HepG2, using suppression subtractive hybridization (SSH). Sequence analysis demonstrated that the
protein is a novel secreting member of the Kazal-type
serine protease inhibitor (
serpin) family, and possesses the basic structure of
serpin, which is highly homologous to
esophageal cancer-related gene 2 (ECRG2). To further elucidate its
biological functions, the Hespintor
protein was expressed and purified. The coding sequence of the Hespintor Kazal domain was cloned into the prokaryotic expression vector, pET-40b(+), and was then transformed into host bacteria (Escherichia coli) Rosetta (DE3). The optimally expressed
recombinant fusion protein, Hespintor-Kazal, with a molecular weight of 42 kDa was obtained by 0.25 mmol/l isopropyl β-D-1-thiogalactopyranoside (
IPTG) induction at 30˚C for 5 h. Western blot analysis was performed to further confirm the specificity of the
recombinant protein, Hespintor-Kazal. The
recombinant fusion protein, Hespintor‑Kazal, was expressed in the host bacteria in the form of an inclusion body. Two-step
metal chelating affinity chromatography and
anion exchange chromatography columns were used to purify the
recombinant protein. The preliminary activity identification results revealed that the purified
recombinant fusion protein, Hespintor-Kazal, specifically inhibited the hydrolysis activity of
trypsin, suggesting that Hespintor has potential value as a novel
antitumor drug.