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The Secret of Genetic Scissors: How do restriction enzymes cut DNA accurately?
In the world of molecular biology, genetic scissors play an indispensable role. These specialized enzymes, called restriction enzymes, are able to cut DNA with precise precision. The working principles and historical background of restriction enzymes are important topics of ongoing research and exploration in the scientific community.
The function of restriction enzymes is involved in the defense mechanisms of bacteria and archaea that destroy foreign viral DNA.
Restriction enzymes (also called restriction endonucleases or REases) are a special class of enzymes that can cut DNA near specific recognition sites. These enzymes are mainly found in bacteria and archaea, and play a defensive role against foreign viruses. Inside a prokaryotic cell, restriction enzymes selectively cut foreign DNA in a process called restriction digestion. The host DNA is protected by enzymes called modifying enzymes, such as methyltransferases, which can modify the host DNA and prevent it from being cut by restriction enzymes. Together, these two processes constitute the restriction modification system. After decades of research, there are now more than 3,600 known restriction endonucleases, most of which have been studied in detail and many are even commercially available.
History of restriction enzymes The concept of restriction enzymes was first discovered in the 1950s by Salvador Luria, Jean Weigle and Giuseppe Bertani, who were studying bacteriophage lambda that infects bacteria and noticed that certain bacterial strains were able to reduce the bioavailability of these phages. active. Therefore, these bacterial strains are called host-restricted. Further research revealed that the restriction was caused by an enzyme specifically called a restriction enzyme. In 1970, Hamilton O. Smith and others isolated and identified the first type II restriction enzyme HindII from Haemophilus influenzae, which led to the application of restriction enzymes in laboratories beginning to receive attention.The discovery of restriction enzymes allowed DNA to be manipulated, leading to the development of recombinant DNA technology, which has a wide range of applications, aiding in the mass production of proteins such as human insulin.
Operation of the recognition site
Restriction enzymes have the ability to accurately recognize specific nucleotide sequences and produce double-stranded cuts at that sequence. These recognition sequences generally consist of 4 to 8 nucleotides and influence their frequency of occurrence in the genome. Many restriction enzymes recognize sequences that are palindromic, meaning that the sequence is identical when read forward and backward.
Classification and types of restriction enzymes
There are five natural classifications of restriction endonucleases: types I, II, III, IV, and V, based on their composition, cofactor requirements, and characteristic signatures of their target sequences. Outside the laboratory, type II restriction enzymes are the most common and are relatively easy to control in the process of recognizing sequences and cutting, which allows scientists to easily perform genetic manipulation.
The rise of artificial restriction enzymes
With the advancement of genetic engineering technology, the emergence of artificial restriction enzymes has provided more possibilities for gene manipulation. By fusing natural or engineered DNA-binding domains to nuclease domains, scientists can design restriction enzymes that target specific DNA sequences. These artificial restriction enzymes such as zinc finger nucleases (ZFNs) have been widely used in gene editing, and even the recent CRISPR-Cas9 system has revolutionized the way genomes are manipulated.
Currently, research on restriction enzymes is still ongoing, and their application potential is still great. From gene cloning, protein production to disease treatment, the existence of restriction enzymes brings unlimited possibilities to the future of biotechnology and genetic engineering. Faced with these scientific advances, we can't help but wonder: How will the future development of genetic manipulation technology change human medicine and lifestyle?
