Figure 9.17 shows three posttranslational steps required to produce the sugar-regulating hormone insulin from the starting polypeptide product preproinsulin.

Recombinant human insulin (made by inserting human DNA encoding insulin into E. coli) is one of the most widely used recombinant pharmaceutical products in the world. What segments of the human insulin gene are used to create recombinant bacteria that produce human insulin?

Key Concepts

Posttranslational Modifications

Posttranslational modifications are chemical changes that occur to a protein after its synthesis. In the case of insulin, these modifications include the cleavage of the preproinsulin precursor to form proinsulin, followed by the removal of the C-peptide to produce active insulin. Understanding these steps is crucial for comprehending how the final functional hormone is generated from its initial polypeptide form.

Recombinant DNA Technology

Recombinant DNA technology involves combining DNA from different sources to create new genetic combinations. In the production of recombinant human insulin, the gene encoding insulin is inserted into bacterial plasmids, allowing bacteria like E. coli to produce the hormone. This technology is fundamental in biotechnology and medicine, enabling the mass production of proteins that are otherwise difficult to obtain.

Gene Segments in Insulin Production

The human insulin gene consists of coding regions (exons) and non-coding regions (introns). For recombinant insulin production, only the exons that code for the insulin peptide are used, as introns are typically removed during mRNA processing. Understanding which segments of the insulin gene are necessary for producing functional insulin is essential for designing effective recombinant DNA constructs.