We constructed a cold induced expression vector in Escherichia coli cells that consists of a histidine tag sequence for nickel chelate affinity purification, IgG-binding domain of protein A(ZZ-domain) and the multiple cloning sites. The role of ZZ-domain as a solubilizing partner at 15 degrees C was demonstrated by expressing the imidazopyrazinone-type luciferases of Renilla, Oplophorus, Coussia, and Vargula (Cypridina) as well as the calcium-binding photoproteins and firefly luciferase. The fused protein with ZZ-domain was expressed efficiently as a soluble form in the cytoplasm of E. colt cells at low temperature. (c) 2008 Elsevier Inc. All rights reserved.