Restriction enzyme
Enzymes that cut DNA at specific sites, enabling genetic manipulation.
Restriction enzymes, also known as restriction endonucleases, REases, ENases, or restrictases, are enzymes that cleave DNA into fragments at or near specific recognition sites called restriction sites. They are found in bacteria and archaea, where they provide a defense mechanism against invading viruses by selectively cutting up foreign DNA in a process called restriction digestion, while host DNA is protected by a modification enzyme. These enzymes are a vital tool in molecular cloning and are routinely used for DNA modification in laboratories.
- number_studied_in_detail
- approximately 600-800
Lore & Background
The term restriction enzyme originated from studies of phage λ, a virus that infects bacteria, and the phenomenon of host-controlled restriction and modification. This phenomenon was first identified in work done in the laboratories of Salvador Luria, Jean Weigle, and Giuseppe Bertani in the early 1950s. It was found that a bacteriophage λ that grows well in one strain of Escherichia coli, such as E. coli C, when grown in another strain like E. coli K, could have its yields drop significantly, by as much as three to five orders of magnitude. In the 1960s, work in the laboratories of Werner Arber and Matthew Meselson showed that the restriction is caused by an enzymatic cleavage of the phage DNA, and the enzyme involved was termed a restriction enzyme.
Reader's Guide
Restriction enzymes are fundamental to molecular biology and biotechnology. Their discovery enabled the manipulation of DNA, leading to the development of recombinant DNA technology. This technology has many applications, including the large-scale production of proteins such as human insulin used by diabetic patients. The 1978 Nobel Prize for Physiology or Medicine was awarded to Werner Arber, Daniel Nathans, and Hamilton O. Smith for their work in the discovery and characterization of restriction enzymes. The first type II restriction enzyme, HindII, was isolated and characterized in 1970 from the bacterium Haemophilus influenzae. Type II enzymes are the most commonly used as a molecular biology tool because they cleave DNA at the site of their recognition sequence. Restriction enzymes are routinely used for DNA modification in laboratories and are a vital tool in molecular cloning.
Did You Know?
- More than 3,600 restriction endonucleases are known, representing over 250 different specificities.
- Restriction enzymes likely evolved from a common ancestor and became widespread via horizontal gene transfer.
- The first type II restriction enzyme, HindII, was isolated from the bacterium Haemophilus influenzae in 1970.
- Restriction enzymes are found in bacteria and archaea and provide a defense mechanism against invading viruses.
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