Directed evolution is a method used in protein engineering to harness the power of Darwinian selection to evolve proteins with desirable properties not found in nature. Protein engineering is the application of science, mathematics, and economics to the process of developing useful or valuable proteins. ... Alternative meaning Natural Selection (computer game). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

A typical directed evolution experiment involves two steps:

1. Library creation: The gene encoding the protein of interest is mutated and/or recombined at random to create a large library of gene variants. Techniques commonly used in this step are error-prone PCR and DNA shuffling. Wikipedia does not yet have an article with this exact name. ... DNA shuffling, also known as sexual PCR, is a way to rapidly propagate beneficial mutations in a directed evolution experiment. ...

2. Library screening: The library is screened by the researcher using a high-throughput screen to identify mutants or variants that possess the desired properties. Winner mutants identified in this way then have their DNA sequenced to understand what mutations have occurred. This article is concerns biological mutants; for fictional aspects see Mutant (fictional) A mutant is an individual, organism, or new genetic character arising or resulting from an instance of mutation, which is a sudden structural change within the DNA of a gene or chromosome of an organism resulting in the... The general structure of a section of DNA Deoxyribonucleic acid (DNA) is a nucleic acid —usually in the form of a double helix— that contains the genetic instructions specifying the biological development of all cellular forms of life, and most viruses. ...

The evolved protein is then characterized using biochemical methods.

This approach allows an increase in functional density of the protein of interest, as it allows the identification of interesting mutants using The Blind Watchmaker. As such it can be more powerful than the standard method of using site-directed mutagenesis based on X-ray crystallography data. Cover The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design is a 1986 book by Richard Dawkins in which he presents an explanation of, and argument for, the theory of evolution by means of natural selection. ... (in vitro mutagenesis) Site-directed mutagenesis is a molecular biology technique in which a mutation is created at a defined site in a DNA molecule, usually a circular molecule known as a plasmid. ... X-ray crystallography is a technique in crystallography in which the pattern produced by the diffraction of X-rays through the closely spaced lattice of atoms in a crystal is recorded and then analyzed to reveal the nature of that lattice. ...

Most directed evolution projects seek to evolve properties that are useful to humans in an agricultural, medical or industrial context. It is thus possible to use this method to optimize properties that were not selected for in the original organism. This may include catalytic specificity, thermostability and many others.

In nature

Some hypothesize that organisms can direct their mutations during times of stress to areas of particular genomic instability. For example, an E Coli might have error-prone DNA segments for genes which are likely to mutate into useful antibiotic resistance genes. This would work in concert with programmed evolution to trigger desirable changes. However, the hypothesis is very contentious and is still largely unverified. Programmed evolution is an evolutionary process akin to natural selection. ...

External links

• [1] - This is the web-page of the Frances H. Arnold Research Group. One of the most important directed evolution laboratories.

Further reading

1. Yuan, L., I. Kurek, et al. (2005). "Laboratory-directed protein evolution." Microbiology and Molecular Biology Reviews 69(3): 373-+.

2. Arnold, F. H. (1998). "Design by directed evolution." Accounts of Chemical Research 31(3): 125-131.