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The RM system was first discovered by Salvatore Luria and Mary Human in 1952 and 1953. [1] [2] They found that a bacteriophage growing within an infected bacterium could be modified, so that upon their release and re-infection of a related bacterium the bacteriophage's growth is restricted (inhibited; also described by Luria in his autobiography on pages 45 and 99 in 1984). [3]
A restriction enzyme or restriction endonuclease is a special type of biological macromolecule that functions as part of the "immune system" in bacteria.One special kind of restriction enzymes is the class of "homing endonucleases", these being present in all three domains of life, although their function seems to be very different from one domain to another.
Different restriction enzymes acting on different recognition sites produce different DNA fragments. The term restriction enzyme originated from the studies of phage λ, a virus that infects bacteria, and the phenomenon of host-controlled restriction and modification of such bacterial phage or bacteriophage. [12]
This article contains a list of the most studied restriction enzymes whose names start with C to D inclusive. It contains approximately 80 enzymes. The following information is given: Enzyme: Accepted name of the molecule, according to the internationally adopted nomenclature [1] [2], and bibliographical references.
This article contains a list of restriction enzymes whose names start with A and have a clearly defined cutting site. The following information is given for each enzyme: Name of Restriction Enzyme : Accepted name of the molecule , according to the internationally adopted nomenclature , [ 1 ] [ 2 ] and bibliographical references .
Type III site-specific deoxyribonuclease (EC 3.1.21.5, type III restriction enzyme, restriction-modification system) is an enzyme. [1] This enzyme catalyses the following chemical reaction. Endonucleolytic cleavage of DNA to give specific double-stranded fragments with terminal 5'-phosphates
Several databases exist for restriction sites and enzymes, of which the largest noncommercial database is REBASE. [5] [6] Recently, it has been shown that statistically significant nullomers (i.e. short absent motifs which are highly expected to exist) in virus genomes are restriction sites indicating that viruses have probably got rid of these motifs to facilitate invasion of bacterial hosts. [7]
The combination of both provide is a defense mechanism against invading viruses. [3] The methyltransferase and endonuclease are encoded as two separate proteins and act independently. In the PstI system, the genes are encoded on opposite strands and hence must be transcribed divergently from separate promoters .