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

A research scientist is interested in producing human insulin in the bacterial species E. coli. Will the genetic code allow the production of human proteins from bacterial cells? Explain why or why not.

Key Concepts

Genetic Code Universality

The genetic code is nearly universal across all living organisms, meaning that the same codons typically code for the same amino acids in different species. This universality allows for the potential expression of human genes in bacterial systems, as the basic machinery for translation is conserved. However, there are exceptions and variations in certain organisms that can affect protein synthesis.

Posttranslational Modifications

Posttranslational modifications are chemical changes that occur to a protein after its synthesis, which are crucial for its functionality. In the case of insulin, specific modifications such as cleavage and folding are necessary for its activity. Bacteria like E. coli lack the cellular machinery to perform these complex modifications, which can hinder the production of fully functional human proteins.

Gene Cloning and Expression Systems

Gene cloning involves inserting a gene of interest into a vector, which can then be introduced into a host organism for expression. E. coli is a common expression system due to its rapid growth and ease of manipulation. However, while E. coli can produce the polypeptide chain of human proteins, the lack of proper posttranslational modification capabilities may prevent the production of biologically active forms of those proteins.