Objective To construct a prokaryotic high-level expression system for human NT-proBNP (amino-terminal pro-brain natriuretic peptide) and establish the working standard for immunoassay. Methods According to the frequency of E. coli codons

an E. coli favorite DNA fragment

encoding amino acids sequence identical to that of the wild type NT-proBNP was cloned into plasmid pET32a and pET42a by synthesized oligoes and GeneSOEing PCR techniques. The NT-proBNP protein was isolated by cation exchange

his-tag affinity column

GST affinity chromatograph and digested by enterokinase. Immunoreactivity and stability of the protein were identified by using NT-proBNP test kit (Roche.Ltd). Results After induced by IPTG

the NT-proBNP was expressed efficiently as soluble protein in E. coli cells. The purified NT-proBNP (98.3%) was immunoreactive and stable. Conclusion The prokaryotic high-level expression vector of human NT-proBNP was successfully constructed. A recombinant protein NT-proBNP suitable for standards of immunodetection was obtained.