pCold ProS2 DNA is a fusion cold-shock expression vector whichfeatures Protein S, a soluble tag from Myxococcus xanthus. Protein S, which is comprised of 173 amino acid residues, is a very stable soluble protein present in a spore surface coat of Myxococcus xanthus. A fusion of target protein with the ProS2 Tag, a tandem repeat of 2 N-terminal domain (NTD) sequences of Protein S, will induce the stability and solubility of the fusion protein.

The pCold ProS2 DNA Vector consists of the cspA promoter plus additional downstream sequences including a 5" untranslated region (5" UTR), translation enhancing element (TEE), his-tag sequence, ProS2 tag, and multiple cloning site (MCS). A lac operator is inserted downstream of the cspA promoter to ensure strict regulation of expression. Additionally, recognition sites for HRV 3C Protease, Thrombin, and Factor Xa are located between the ProS2 Tag and MCS and function to facilitate tag removal from the expressed fusion protein. Most E. coli strains can serve as expression hosts. The pCold ProS2 DNA vector provides cold-shock technology for high yield protein expression to facilitate correct protein folding, thus enabling efficient soluble protein production for otherwise intractable target proteins.Elucidation of protein structure and function maintains an important role in postgenomic sequencing and analysis studies. An efficient protein production system is critical for obtaining large amounts of correctly folded recombinant protein for study. E. coli expression systems, which are used extensively for the production of recombinant proteins, offer two major advantages over other types of expression systems: 1) ease of use, and 2) low cost. However, some recombinant proteins do not fold correctly during expression in E. coli and result in deposits of inactive insoluble protein termed "inclusion bodies."Takara Bio has developed the pCold DNA vectors, a series of novel protein expression vectors in collaboration with Prof. Masayori Inouye (University of Medicine and Dentistry of New Jersey, USA). The pCold Vectors provide increased in vivo protein yield, purity, and solubility for expressed recombinant proteins using "cold shock" technology. More specifically, the cspA (cold shock protein A) promoter and related elements have been incorporated into these vectors to up-regulate target protein production at lowered incubation temperatures (37–15°C). This temperature drop also suppresses expression of other cellular proteins and temporarily halts overall cell growth. This process allows high-yield, high-purity expression of target proteins (up to 60% of cellular protein), and increased solubility as compared with conventional E. coli expression systems.