[Molecular Cloning,Sequence Analysis,and Expression of Pepsinogens C Gene from Adult Alligator Sinensis Stomach]

Objective To investigate the molecular clone and structural features of pepsinogen C(PGC) gene in the stomach of Alligator sinensis,explore the phylogenetic relationships and tissue distribution,and analyze the variation of PGC expression in the stomachs of adult Alligator sinensis at different life stages. Methods The full-length cDNA of PGC gene of Alligator sinensis was cloned by reverse transcription polymerase chain reaction and rapid amplification of cDNA ends and then sequenced.The physical and chemical parameters and advanced structures of the PGC protein were predicted by bioinformatics methods and tools.The PGC amino acid sequences of the Alligator sinensis and other vertebrates were compared by Clustal X software.The neighbor-joining phylogenetic tree was built by MEGA 6 software.Immunohistochemistry was used to locate PGC in the gastric mucosa of Alligator sinensis.The variation of the PGC mRNA levels in the stomach at different life stages was detected by quantitative real-time polymerase chain reaction.Results Reverse transcription polymerase chain reaction and rapid amplification of cDNA ends revealed a 1568 bp cDNA full-length sequence containing 1167 bp open reading frame,which encoded 388 amino acids.The PGC gene of Alligator sinensis had been deposited in the GenBank Data Libraries under the accession number of KY799383.Bioinformatics analysis predicted that the Alligator sinensis PGC had a theoretical relative molecular mass of 41 998 with a theoretical isoelectric point of 4.16.In addition,the three-dimensional structure of the PGC was constructed by homology modeling to predict its active site with two essential aspartyl residues and six essential cysteine residues involved in forming three disulphide bonds.The neighbor-joining phylogenetic tree of vertebrates from the amino acids sequences of PGC showed all crocodiles were clustered as a group,and the PGC of Alligator sinensis was the closest to Alligator mississippiensis.Alligator sinensis PGC was specifically expressed in the gastric mucosa,and its expressions significantly differed during reproduction and hibernation significantly(P<0.05).Conclusions Alligator sinensis PGC gene is highly conserved in evolution.Its protein is a gastric specific digestive proteinase that belongs to a aspartic proteinase family.