The purpose of the invention is to provide a novel purification system allowing the efficient and economical production and purification of a recombinant fused protein, whereby the elution time at a low temperature can be reduced, since it has been a problem to be solved in the existing purification method using dockerin and cohesin. In this purification system, a dockerin polypeptide characterized in that the 14th amino acid in the subdomain 2 of dockerin originating from Clostridium josui is substituted with another amino acid, and a method for purification of a recombinant fused protein are provided.
