Fig. 1

Tertiary structure of TsTryp and phylogeny of trypsin in 22 organisms by NJ method. a Online analysis of the NCBI and SMART databases showed that TsTryp had two identical and independent trypsin-like serine protease domains (Tryp_SPc). b The NCBI-Cn3D online website was used to conduct homology modeling for TsTryp and predict its tertiary structure. The secondary structure of TsTryp comprises alpha-helices (green cylinders), beta-strands (brown sheets) and random coils (gray strands). TsTryp had two similar trypsin-like domains; the three enzyme active sites of Asp, Ser and His are shown as yellow spheres. c Phylogenetic tree of the trypsin of Trichinella spiralis and other nematodes were constructed by NJ method in MEGA7.0 software. NJ, Neighbor-joining; TsTryp, T. spiralis trypsin