Abstract: Objective To study the effect of different point mutations in exon 3 on the structure of PAX9 protein. Methods The DNA and amino acid sequence information of exon 3 mutations of human PAX9 gene were retrieved by Pubmed and ClinVar databases, and the amino acid sequences affected by exon 3 mutations were compared in different species and different PAX genes. Phyre2 and RaptorX were used to predict and analyze the threedimensional structure of the amino acid sequence. Results The amino acid sites of the PAX9 gene affected by exon 3 mutation were highly conserved. 25, 26, 28, 43, 51, 56, 59, 87, 91 and 143 amino acids participated in the composition of Alpha helix secondary structure. 6, 73, 80, 136, 143, 145, 168 and 172 amino acid sites had strong pathogenicity. Gly6Arg and Pro20Leu would alter the alpha helix secondary structure of the DNA binding region in the PAX9 protein. Other amino acid changes could also alter the space folding and structure of PAX9 protein in different degrees. Conclusion The change of amino acid caused by mutations in exon 3 may cause different changes in the structure of PAX9 protein, which may also be the reason that the phenotype of oligodontia or hypodontia caused by different PAX9 mutations are not exactly the same.

Key words: exon 3, mutation, PAX9, protein structure, bioinformatic analysis