Establishing Prokaryotic Expression System of Angiotensin-Converting Enzyme 2 (ACE2) gene in pigs

Xiao, Hang; Nie, Xin-Tian; Ji, Xiao-Xia; Yan, Shu-ping; Zhu, Bin; Zhang, Yuan-Shu

In this paper, ACE2 gene of pigs was cloned and the purified protein was obtained via the prokaryotic expression system. Polyclonal antibody of high titer and sensitivity was obtained using Wastar rats immunization method and is then used to determine of the expression of ACE2 using immunohistochemistry. The sequence of ACE2 in pigs covered 2418 nucleotides and coded 805 amino acid (aa) residues. Sequence homology analysis showed that the ACE2 sequence in pigs is highly conserved among species at the nucleotide and amino acid levels. Genetic evolution analysis revealed that ACE2 gene in pigs has the shortest genetic distance with that in goats while residing in a totally different branch from that in zebra fishes. Analysis of protein structure predicted that ACE2 protein is a transmembrane secreted protein with high hydrophilicity, containing a signal peptide sequences locating between 1aa to 17aa. The ACE2 fusion protein expressed (under the induction with 1.0 mmol/L IPTG for 10 h) was of approximately 100 kDa and mainly existed in inclusion body. Wastar rats immunization showed that the titer of the anti-ACE2 antiserum in rats was 1: 3200. Western blot showed that the antibody binds specifically. Immunohistochemistry showed that the ACE2 protein was expressed in all major tissues of pigs. It is the first time that polyclonal antibody of ACE2 in pigs was obtained and the expression of ACE2 was confirmed. These results will provide a basis for investigating on ACE2’s biological activity in pigs.