Cloning and Expression of the Gene Encoding the GMP Reductase of Escherichia coli MC4100

The gene encoding GMP reductase was cloned from E. coli MC4100 by polymerase chain reaction (PCR). This gene comprises 1 044 bp, and it encodes a polypeptide of M r 37 437. The gene was inserted into the downstream of the T7 promoter of plasmid pET 16b and recombinant pEXP1 was obtained, which was then transformed into E. coli BL21(DE3). There was overexpression under the induction by IPTG. Enzyme assay showed that the activity of GMP reductase increased by 80~85 fold in the recombination strain.