2.11 Restriction Endonuclease: Nomenclature, Types,
and Characteristics
Bacteria possess restriction enzymes that nick and eliminate genetic information
entering the cell in virus or DNA form. In 1970, H. O. Smith, and D. Nathans
succeeded for the first time in purifying a restriction enzyme. More than 300 have
been discovered since then.
One restriction enzyme is deoxyribonuclease, which recognizes DNA’s specific
base sequence and passes on the DNA chain. It is through this enzyme that long and
thin chromosomal DNA is cut into various fragments, allowing specific pieces to be
obtained. For the names of restriction enzymes, a capital letter representing the
genus of the bacterium producing it is used, followed by two lower case letters from
the species; the three letters are represented in italics. When the origin is listed, the
name of the strain or plasmid is written afterwards. When two or more enzymes
have been isolated from the same strain, Roman numerals are added to distinguish
between them. For example, an example isolated from Eschericia coli, which
possesses the antibiotic resistance factor R, would be labeled Eco RI, while
examples isolated from Haemophilus influenza include Hind I, Hind II, and Hind III
(Roberts et al. 2003).
For most bacteria, methylated bases within their DNA possess characteristic
shapes, and a mechanism exists to distinguish and secrete different forms of DNA
entering the cell from its own DNA. Modification methylase and restriction
endonuclease are both part of this mechanism.
Modification methylase performs the role of producing the species’s specific
methylation form within the characteristically shortened base sequence in the host
cell’s DNA. This methylated base sequence is repeated several times in the host cell
DNA. The methyl group in this sequence remains in its state throughout the cell’s
lifespan. In contrast, restriction endonuclease clips two different DNA chains when
this characteristic base pair is not methylated.
When DNA becomes introduced through infection of the bacteria by a phase, the
restriction enzyme distinguished whether it is self-modeled or outside-modeled
DNA. If it is not a modified version of the cell’s own model, the DNA is cut and
deactivated, preventing reproduction of the outside phage.
The restriction and modification phenomenon was first reported in 1952 by
Bertani and Weigle; an example is presented in Fig. 2.20. When a lambda phage
(kÁC) growth on the E. coli’s C strain infected its K strain, breeding was restricted
and only around 2/10,000 of the infecting phage’s plaque formed. When the K
strain was then infected with the lambda phage (kÁK) breeding on the K starin
(kÁK), however, efficient plaque formation occurred. When the kÁK was bred on the
C strain and used to infect the K strain, the plaque formation rate was again around
2/10,000, showing that the k phage’s host range was not the result of mutation. In
the 1960s, Arber concluded, based on the fact that this phenomenon was accompanied by DNA cutting and that uncut DNA was modified by methylation, that this
2.11 Restriction Endonuclease: Nomenclature, Types, and Characteristics
47
and Characteristics
Bacteria possess restriction enzymes that nick and eliminate genetic information
entering the cell in virus or DNA form. In 1970, H. O. Smith, and D. Nathans
succeeded for the first time in purifying a restriction enzyme. More than 300 have
been discovered since then.
One restriction enzyme is deoxyribonuclease, which recognizes DNA’s specific
base sequence and passes on the DNA chain. It is through this enzyme that long and
thin chromosomal DNA is cut into various fragments, allowing specific pieces to be
obtained. For the names of restriction enzymes, a capital letter representing the
genus of the bacterium producing it is used, followed by two lower case letters from
the species; the three letters are represented in italics. When the origin is listed, the
name of the strain or plasmid is written afterwards. When two or more enzymes
have been isolated from the same strain, Roman numerals are added to distinguish
between them. For example, an example isolated from Eschericia coli, which
possesses the antibiotic resistance factor R, would be labeled Eco RI, while
examples isolated from Haemophilus influenza include Hind I, Hind II, and Hind III
(Roberts et al. 2003).
For most bacteria, methylated bases within their DNA possess characteristic
shapes, and a mechanism exists to distinguish and secrete different forms of DNA
entering the cell from its own DNA. Modification methylase and restriction
endonuclease are both part of this mechanism.
Modification methylase performs the role of producing the species’s specific
methylation form within the characteristically shortened base sequence in the host
cell’s DNA. This methylated base sequence is repeated several times in the host cell
DNA. The methyl group in this sequence remains in its state throughout the cell’s
lifespan. In contrast, restriction endonuclease clips two different DNA chains when
this characteristic base pair is not methylated.
When DNA becomes introduced through infection of the bacteria by a phase, the
restriction enzyme distinguished whether it is self-modeled or outside-modeled
DNA. If it is not a modified version of the cell’s own model, the DNA is cut and
deactivated, preventing reproduction of the outside phage.
The restriction and modification phenomenon was first reported in 1952 by
Bertani and Weigle; an example is presented in Fig. 2.20. When a lambda phage
(kÁC) growth on the E. coli’s C strain infected its K strain, breeding was restricted
and only around 2/10,000 of the infecting phage’s plaque formed. When the K
strain was then infected with the lambda phage (kÁK) breeding on the K starin
(kÁK), however, efficient plaque formation occurred. When the kÁK was bred on the
C strain and used to infect the K strain, the plaque formation rate was again around
2/10,000, showing that the k phage’s host range was not the result of mutation. In
the 1960s, Arber concluded, based on the fact that this phenomenon was accompanied by DNA cutting and that uncut DNA was modified by methylation, that this
2.11 Restriction Endonuclease: Nomenclature, Types, and Characteristics
47