Abstract：Bioinformatics analysis revealed that a functionally unknown sequence, named as Ttx31, from the ?-amylase/pullulanase of Thermoanaerobacter thermohydrosulfuricusits could encode a novel carbohydrate binding module (CBM), but its’ binding specificity remains unknown. The sequence of Ttx31 was obtained by colony PCR from Thermoanaerobacter thermohydrosulfuricus and was cloned into the expression vector pET22b (+) to construct a recombinant plasmid named as pEX31. Sequence analysis revealed that pEX31 contained the correct Ttx31. After transforming pEX31 into Escheriachia coli Tuner, the recombinant protein, TtX31, was induced by IPTG and purified. The interaction between TtX31 and sugars was investigated by SDS-PAGE and non-denaturing affinity gel electrophoresis. Data obtained here showed that TtX31 displayed binding specificity for dextrin other than soluble starch, pullulan, and amylopectin. This finding indicates that TtX31 could be a functional novel CBM with dextrin binding activity.
