Chemical synthesis of a gene coding for human angiogenin, its expression in Escherichia coli and conversion of the product into its active form

A synthetic gene coding for human angiogenin was synthesized by solid support phosphoramidite chemistry as eight long oligodeoxynucleotides which were subsequently assembled and cloned in Escherichiu coli. The gene was designed to use codons found in highly expressed E. coli proteins. A pBR322-derived expression vector was constructed containing the E. coli trp promoter, the ribosome-binding site of the bacteriophage λ cII gene, the angiogenin coding sequence, and the transcription terminator region of the E. coli rmB operon. Under tryptophan deprivation, angiogenin was strongly expressed in E. coli cells at a yield of 5–10% of total protein. The eukaryotic protein was found to be insoluble but could be easily renatured and purified. The purified angiogenin was demonstrated to be active as an angiogenic factor and exhibited a characteristic RNase activity.