Abstract：It is meaningful for resistance management to study the resistance mechanism of Asian corn borer (Ostrinia furnacalis) to Cry1Ab. cDNA of aminopeptidase N (APN) from Cry1Ab toxin susceptible and resistant strains of Asian corn borer was cloned and sequenced. Ofapn3, a member of aminopeptidase N families, was identified. It contained 3 591 nucleotides with a 3 045 bp open reading frame that encoded 1 014 amino acids. Putative protein sequences included 8 and 4 potential N- and O-linked glycosylation sites and a zinc metal binding site motif of HEXXHX18E, which was typical of the active sites of the zinc-dependent metalloproteases, and a highly conserved GAMEN motif, which was to form part of the active site. The sequences had a cleavable N-terminal signal peptide with 18 amino acids and a glycosylphosphatidylinositol (GPI) anchor signal peptide with 22 amino acids in C-terminal, which were also typical characters of lepidopteran APN proteins. Sequence analysis indicated that the deduced protein sequences were most similar to Onapn3 (GenBank accession No.ABL01483) from Ostrinia nubilalis with 96.6% sequence identity. The predicted protein molecular weights and isoelectric points were 115.1 kD and 4.44, respectively. Forty nucleotide differences were observed in the open reading frames which translated into 10 amino acid differences in the putative protein sequences. The sequences reported in this paper have been deposited in the GenBank database (accession No. EF538427and EU137839 for Ofapn3 from Cry1Ab-resistant strain ACB-AbR and susceptible strain ACB-BtS).
