Synthetic genes for human insulin A and B chains were cloned separately in plasmid pBR322. The cloned synthetic genes were then fused to an Escherichia coli #-galactosidase gene to provide efficient transcription and translation and a stable precursor protein. The insulin peptides were cleaved from Pgalactosidase, detected by radioimmunoassay and purified. Complete purification of the A chain and partiaf purification of the B chain were achieved. These products were mixed, reduced, and reoxidized. The presence of insulin was detected by radioimmunoassay.Recently improved methods of DNA chemical synthesis, combined with recombinant DNA technology, permit the design and relatively rapid synthesis of modest-sized genes that can be incorporated into prokaryotic cells for gene expression. The feasibility of this general approach was first demonstrated by the synthesis, and expression in Escherichia col, of a gene for the mammalian peptide somatostatin (1).Following the precursor protein approach used for somatostatin (1), the experimental design for this work was such that the insulin peptide chains would be made in vio as short tails joined by a methionine to the end of ,3-galactosidase. After synthesis, the insulin chains, which contain no methionine, can be cleaved off efficiently by treatment with cyanogen bromide. We deliberately chose to construct two separate bacterial strains, one for each of the two peptide chains of insulin: the 21-amino-acid A chain and the 30-amino-acid B chain. In native insulin, the two chains are held together by two disulfide bonds, and methods have been available for years for joining the chains correctly, in vitro, by air oxidation (2). The efficiency of correct joining has been variable and often low. However, by using S-sulfonated derivatives and an excess of A chain, 50-80% correct joining has been obtained (3).The synthetic plan and chemical synthesis of the DNA fragments coding for the A and B chains of human insulin were described in a previous paper (4) and were summarized in Fig. 1 Enzymes and DNA Preparations. T4 DNA ligase and T4 polynucleotide kinase were purified as described (6). Restriction endonuclease EcoRI was purified by the procedure of Greene et al. (7); HindIII was purified by a method developed by D. Goeddel (unpublished). Restriction endonuclease BamHI was purchased from Bethesda Research (Rockville, MD); E. coli alkaline phosphatase was purchased from Worthington.Plasmids, including pBR322 (8), were isolated by a published procedure (9) with some modifications. The chemical synthesis of the deoxyoligonucleotides (figure 1 of ref. 4) has been described (4). Xplac5 DNA was isolated as described (10).The following reaction buffers were used: kinase buffer, 60 mM Tris-HCl, pH 8/15mM 2-mercaptoethanol/10 mM MgCl2; ligase buffer, 20mM Tris-HCl, pH 7.5/10mM dithiothreitol/10 mM MgCl2; BamHI buffer, 20 mM Tris-HCl, pH 7.5/7 mM MgCl2/2 mM 2-mercaptoethanol; EcoRI-HindIll buffer, BamHI buffer containing 50 mM NaCl; and phosphatase buffer, 50 mM Tris-HCl, pH...

The biological importance and practical significance of phosphate esters and their analogues have been the major driving forces for research in various areas of synthetic organic phosphorus chemistry. In this Account, the authors' studies on the development of a comprehensive H-phosphonate methodology and the underlying chemistry for the preparation of biologically important phosphate esters and their analogues are briefly discussed.

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A -rapid chemical procedure has been developed and used for the synthesis of 29 oligodeoxyribonucleotides to build synthetic genes for human insulin, The gene for insulin B chain, 104 base pairs, and the one for A chain, 77 base pairs, were designed from the amino acid sequence of human polypeptides. They bear single-stranded cohesive termini for the EcoRI and BamHI restriction endonucleases and are designed to be inserted separately into a pBR322 plasmid. Ihe synthetic fragments, deca-to pentadecanucleotides, were synthesized by a block phosphotriester method with trinucleotides as building blocks. Final purification was by high-performance liquid chromatography. All 29 oligonucleotides were pure and had the correct sequences.In a previous paper we reported production of a functional peptide hormone, somatostatin, in Escherchia coi from a gene of chemically synthesized origin (1). This result demonstrated that a gene, designed from an amino acid sequence, can be synthesized and expressed to produce the peptide in E. coli. However, extension of this technology to production of biomedically valuable polypeptides such as human insulin and growth hormone seemed to be limited by the difficulty of synthesizing longer genes in a reasonable time.Recent improvements in the synthesis of oligodeoxyribonucleotides by the phosphotriester method, such as the rapid synthesis of trimers (2) and the block synthesis of oligonucleotides (3), together with the extensive use of high-performance liquid chromatography for analysis and purification of the DNA fragments, have dramatically reduced the time necessary for construction of DNA fragments. In this paper we report the synthesis of 29 oligodeoxyribonucleotides of defined sequence that can be assembled to form genes for human insulin B and A chains.The overall design of the gene for its incorporation into the plasmid pBR322 was similar to that used for the somatostatin gene (1). Fig. 1 shows the amino acid and nucleotide sequences for human insulin A and B chains. These genes will be fused to E. coli ,-galactosidase gene on plasmid pBR322. Transformation of E. coli with the chimeric plasmid DNA will lead to the synthesis of hybrid polypeptides, including the sequence of amino acids corresponding to human insulin A and B chains. Because human insulin has no methionine residues in the amino acid sequence, the A and B chains can be obtained by cyanogen bromide cleavage of the precursors. After the separate production and purification of the A and B chains, active human insulin will be generated by in vitro formation of the correct disulfide bonds between A and B chains (4, 5).The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. 5765 MATERIALS AND METHODSChemical synthesis of oligodeoxyribonucleotidesMost of the materials and methods used for the synthesis of oligodeoxyribonucleotides were described earlier (6, 7) exc...