(trp promoter/hybrid plasmid/promoter efficiency/modified Shine-

A gene coding for human growth hormone, which consists of 192 amino acids, was chemically synthesized. The synthesis entailed ligating 78 deoxyribooligonucleotides, which had been synthesized on polymer supports by the phos- photriester method with frequently occurring amino acid co- dons of Escherichia coli. The chemically synthesized gene was inserted into an E. coli plasmid downstream from the E. coli trp promoter, with a modified ribosome-binding region car- ried on pBR322. E. coli cells transformed with this recombi- nant plasmid synthesized 2.9 x 106 molecules per cell of hu- man growth hormone upon induction. The induced polypep- tide was identical with natural human growth hormone in size and in immunological properties, as well as in biological activi- ty as examined by the tibial test with hypophysectomized rats. The improvement of techniques in chemical synthesis of deoxyribooligonucleotides has made possible the total syn- thesis of genes of 100-500 nucleotides (1-9). By this tech- nique, genes with designed amino acid sequences can in principle be synthesized, and the products of their expres- sion in bacteria can be examined. In the present work, a gene for human growth hormone (hGH) (10), which contains 191 amino acids and methionine, was totally synthesized by