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How to direct evolution

In David Ackerley’s lab at Victoria University in Wellington, they are using directed evolution to make enzymes with new functions. Here, find out the steps involved in evolving an enzyme.

Directed evolution begins with the bacterial gene that codes for the enzyme and involves several steps:

Step 1: Designing PCR primers

First, you have to design primers that bind to the bacterial DNA. The primers are used during polymerase chain reaction (PCR) to direct the transcription or copying of the gene.

Step 2: Making gene variants

Then you use a ‘sloppy’ or error-prone version of PCR to introduce mutations into the bacterial gene. This step will give you millions of random gene variants.

Introducing mutations into a gene speeds up the evolutionary process.

Step 3: From gene to mRNA to enzyme

You need to translate the genes into proteins.

You can insert the genes into a bacterial plasmid and then introduce them into bacterial cells. The genes are translated into enzymes inside the bacterial cells.

The variations in these genes may cause changes in the amino acid sequence of the enzyme. Any changes in the amino acid sequence of the enzyme can affect its structure and function.

Step 4: Detecting improved enzymes

You need to test whether the enzyme’s function is changed. A lot of gene variants are produced, so you need a test that is simple and easy to do. This is called a screening test.

The screening test allows you to detect enzymes that have new or improved functions. Evolved enzymes can have a wide variety of uses in industry, agriculture or medicine.

Step 5: Using the improved enzyme

If you were working in David Ackerley’s lab, your screening test would be looking for an enzyme that can act on a prodrug to produce a toxic metabolite. If you found an efficient enzyme, it could be used in a new cancer treatment.


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