PCR cloning and expression of the family xylanase gene from Streptomyces olivaceoviridis E-86

Using a simple long-range inverse PCR method, we cloned the GC-rich gene (68%) for an F 10 xylanase from Streptomyces olivaceoviridis E-86. The open reading frame of the cloned gene, fxyn, contained 1431 bp and encoded 477 amino acid residues. FXYN resembled a xylanase of the F 10 family and had two functional domains (a catalytic domain and a substrate-binding domain). Unique triple repeat sequence regions (CLD-C) were located in the substrate-binding domain, which was similar to the xylan-binding domains of xylanase A and that of arabinofuranosidase B from S. lividans. FXYN with a tag that consisted of six histidine residues at the carboxy-terminus was expressed at high levels in Escherichia coli and had the same properties as the native xylanase produced by S. olivaceoviridis. Moreover, the xylan-binding domain of FXYN significantly enhanced hydrolysis of insoluble xylan whereas it had minimal effect on the hydrolysis of soluble xylan.