Abstract：Porcine aminopeptidase N (pAPN) was the receptor protein of a series of virus, such as Transmissible gastroenteritis virus (TGEV) and Porcine epidemic diarrhea virus (PEDV). So this study aimed to probe into the structures and important mutation loci of pAPN gene and provide basis for screening out effective genetic markers of the resistance to viral diarrhea in Meishan pigs (Sus scrofa). The functional regions and important mutation loci were screened out by bioinformatics analysis of the protein structure through PCR, cloning, sequencing and bioinformatics tools. The results showed that the cDNA sequence of pAPN gene (GenBank accession No. KF280271) of Meishan pigs was 2 886 bp in length, including 20 exons, which encoded 961 amino acids. Compared with standard pAPN gene (Accession No. NM_214277.1) sequence in the Genbank database, there were 10-amino acid mutations and 2-amino acid deletions. Six mutations of Phe82Asn, Leu107Phe, Leu108Ile, Ser330Pro, Trp399Arg, and Glu465Gly occurred in the catalytic activity area of APN enzyme. One mutation of Gln747His and 2 deletions of 748Tyr and 749Ser occurred in APN virus combined area. Prediction of protein structure and functional analysis of encoding product showed that pAPN protein was unstable and hydrophilic, without signal peptide, including 1 transmembrane helice (transmembrane region between 12th and 34th amino acid). Secondary structure of pAPN protein mainly contained alpha helix and beta folding. Encoded product was mainly responsible for cell envelope, central intermediary metabolism and biosynthesis of cofactors. One mutation of Gln747His and 2 deletions of 748Tyr and 749Ser might associate with the combination ability of aminopeptidase N and virus. This study analyzed the function and screened out the mutations of pAPN gene, which provides theoretical basis for selecting effective genetic marker of the resistance to viral diarrhea in future.
