Several actinomycetes produce nucleotide 3′-pyrophosphokinase (EC 22.214.171.124), which tansfers the 5′-β, γ-pyrophosphoryl group of ATP or dATP to a variety of purine and pyrimidine nucleotides at their 3′-OH site. To elucidate the expression mechanism and to attempt the use of a gene coding for this enzyme in a heterologous host, we expressed the gene from Streptomyces morookaensis in Escherichia coli. A DNA fragment that included this gene was inserted downstream of the lac promoter in a multicopy plasmid, pUC 119. The resultant plasmid, pUP3, was introduced into E. coli JM 109. When the cells were incubated in the presence of isopropyl-thio-β-D-galactopyranoside (IPTG), the enzyme was found to be secreted into periplasmic space. E. coli cells harboring pUP 312, derived from pUP 3, grew slowly in the presence of IPTG. 3′-Pyrophosphoryl nucleotides were detected in the nucleotide pools of the E. coli cells that produced this enzyme.
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