Cloning and sequence analysis of an acidophilic xylanase (XynI) gene from Aspergillus usamii E001

The full-length cDNA gene that encodes an acidophilic endo-1,4-beta- xylanase XynI of Aspergillus usamii E001 was amplified by rapid amplification of cDNA 3' and 5' ends (RACE) using the total RNA as template and then cloned onto the pUCm-T vector, followed by sequencing. The cloned cDNA is 881 bp in length including 5' and 3' non-encoding regions, as well as a 678 bp of open reading frame (ORF) which encodes an E001 XynI of 188 amino acid residues together with a signal peptide of 37 amino acid residues. The homologies of E001 XynI with xylanases of Aspergillus niger, Aspergillus kawachii, Emericella nidulans and Penicillium funiculosum are 97.8, 92.0, 74.6 and 60.5%, respectively. From a BLAST search result, we concluded that E001 XynI belongs to the glycoside hydrolase family 11. Its three-dimensional structure was predicted using http://swiss-model.expasy.org/on-line programs based on that of the P. funiculosum xylanase (1TE1B) from the family 11. In addition, the complete DNA gene xynI encoding E001 XynI was cloned from the genomic DNA of A. usamii E001 by conventional PCR and ligation-mediated PCR amplification. The cloned xynI is 1,206 bp in length, composed of a promoter region, a 68 bp of intron and two exons when compared with the cDNA of E001 XynI.