How Scientists Taught Bacteria to Make Human Hormones

Genentech's 1979 patent on using engineered DNA to force bacteria to produce human proteins like insulin and growth hormones.

What it covers

This patent describes a method for inserting synthetic DNA into a bacterial plasmid—a small, circular piece of DNA—so the bacteria acts like a factory. The key innovation is using 'codon optimization,' where the synthetic gene is written using the specific DNA 'language' that bacteria prefer, making them much more efficient at reading the instructions to build human proteins. By placing this gene between specific DNA 'cut sites' (restriction endonuclease sites), researchers could reliably insert and express mammalian hormones like somatostatin or insulin chains within a microbial host.

What it doesn't cover

• —Does not cover naturally occurring DNA sequences that have not been synthetically modified for microbial expression.
• —Does not cover the use of non-bacterial hosts like yeast or mammalian cell cultures for protein production.
• —Does not cover the specific medical treatments or clinical applications of the hormones produced.
• —Does not cover gene editing techniques like CRISPR that modify DNA in place rather than using cloning vehicles.

The clever bit

The inventors realized that bacteria have a 'preference' for certain DNA codes; by rewriting the synthetic gene to use these preferred codons, they drastically increased the amount of human protein the bacteria could produce.

Why it matters

This patent is a cornerstone of the modern biotechnology industry. It provided the legal and technical framework for producing life-saving human proteins, such as synthetic insulin, which replaced the previous, less-effective method of harvesting insulin from the pancreases of slaughtered cows and pigs.

Real-world examples

• 1.Synthetic human insulin (Humulin)
• 2.Human growth hormone production
• 3.Recombinant protein manufacturing platforms