Expression of the Methanobacterium thermoautotrophicum hpt gene, encoding hypoxanthine (guanine) phosphoribosyltransferase, in Escherichia coli

The hpt gene from the archaeon Methanobacterium thermoautotrophicum, encodi ng hypoxanthine (guanine) phosphoribosyltransferase, was cloned by function al complementation into Escherichia coli. The hpt-encoded amino acid sequen ce is most similar to adenine phosphoribosyltransferases, but the encoded e nzyme has activity only with hypoxanthine and guanine. The synthesis of the recombinant enzyme is apparently limited by the presence of the rare argin ine codons AGA and AGG and the rare isoleucine AUA codon on the hpt gene. T he recombinant enzyme was purified to apparent homogeneity.