Cloning and sequence analysis of a novel xylanase gene, Auxyn10A, from Aspergillus usamii

A full-length cDNA sequence, encoding a novel endo-1,4-β-d-xylanase (AuXyn10A) of Aspergillus usamii, was obtained by using rapid amplification of cDNA ends (RACE) methods and cloned into the pUCm-T vector, followed by DNA sequencing. The cDNA gene, designated as Auxyn10A, is 1,235 bp in length harboring 5′- and 3′-non-encoding regions, as well as an ORF of 984 bp that encodes a 19-aa signal peptide, a 6-aa propeptide and a 302-aa mature peptide with a calculated MW of 32,756 Da. The AuXyn10A displays high similarity to the xylanases of Aspergillus niger, Aspergillus kawachii and Aspergillus niger, members of the glycoside hydrolase family 10. Its three-dimensional structure was predicted using programs based on the crystal structure of Penicillium simplicissimum xylanase (1B30_A) from the family 10. The complete DNA gene was cloned from the genomic DNA of A. usamii using conventional PCR and hairpin structure-mediated PCR techniques. The DNA gene is 2,255 bp in length, containing a 510 bp of 5′-flanking promoter region and a 1,745 bp of downstream fragment that consists of ten exons and nine short introns ranging from 52 to 62 bp.