Protein expression vector and utilization thereof

A protein expression vector comprising (a) a nucleotide sequence encoding an IgG(κ) or a trypsin secretory signal peptide, (b) a nucleotide sequence encoding a polyhistidine amino acid sequence, (c) a nucleotide sequence encoding a polypeptide comprising amino acid residues 36–40 of SEQ ID NO:19 (Asp-Asp-Asp-Asp-Lys), wherein said polypeptide is cleavable by an enterokinase, and (d) a cloning site into which a polynucleotide encoding a target protein can be inserted, wherein:

• (a), (b), (c) and (d) are assembled within the vector in the order recited;
• the expression vector further comprises a polynucleotide encoding at least one amino acid residue, wherein said polynucleotide is located between the 3′ end of the polynucleotide encoding the IgG(κ) or the trypsin secretory signal peptide and the 5′ end of the polynucleotide having the nucleotide sequence of (c);
• and
• the polynucleotide encoding at least one amino acid residue is a polynucleotide encoding a polypeptide comprising amino acid residues 24–29 of SEQ ID NO:19 (Leu-Val-His-Gly-Lys-Leu).