PCR cloning and expression of the F/10 family xylanase gene from Streptomyces olivaceoviridis E-86

Using a simple long-range inverse PCR method, we cloned the GC-rich gene (6 8%) for an F/10 xylanase from Streptomyces olivaceoviridis E-86, The open r eading frame of the cloned gene, fxyn, contained 1431 bp and encoded 477 am ino acid residues, FXYN resembled a xylanase of the F/10 family and had two functional domains (a catalytic domain and a substrate-binding domain). Un ique triple repeat sequence regions (CLD-C) were located in the substrate-b inding 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 c onsisted 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 ha d minimal effect on the hydrolysis of soluble xylan.