Endonuclease bacterial

Phospholipase D is widely distributed in bacteria, fungi, plants and animals, and is present in almost all mammalian cells [3]. In mammals, it occurs as alternatively spliced products of two genes (PLD1 andPLD2) (Fig. 3). Most mammalian cells express different levels of both isoforms. Both PLD1 and PLD2 have four conserved sequences (I-IV), and sequences I and IV contain the HXKX4D (HKD) motif that is characteristic of the PLD superfamily, which includes bacterial endonucleases, phospholipid synthases, viral envelope... 

Endonuclease Sequence Recognized Cleavage Sites Shown Bacterial Source... 

Restriction endonuclease A deoxyribonuclease which cuts DNA at specific sequences which exhibit twofold symmetry about a point. Name derives from the fact that their presence in a bacterial cell prevents (restricts) the growth of many infecting bacteriophages. 

Cutting with restriction endonucleases is very useful for moving specific pieces of DNA around from place to place. It s also a useful way to name pieces of DNA. For example, a piece of DNA that is cut from a bigger piece of DNA is often named by size and given a surname that corresponds to the two restriction enzymes that did the cutting—the 0.3-kb EcoRI-BamHI fragment. Restriction enzymes themselves are named for the bacterial strains from which they were initially isolated. 

PUTTING YOUR DNA INTO A VECTOR Vectors are specialized pieces of DNA used to move other pieces of DNA around. Modern vectors are usually either bacterial plasmids or viral genomes. The act of isolating your DNA in the first place usually involves putting it into a vector and then selecting the vector that has your DNA in it. DNA pieces (called inserts when they are placed in a vector) are usually placed in vectors using restriction endonucleases. The vector is cut with two restriction enzymes of different specificity (Fig. 6-3). This removes a... 

Restriction endonucleases are bacterial enzymes that cleave DNA at sequence specific sites. They were first discovered in 1970 [19]. Almost 2000 restriction enzymes have been identified since, and several hundred of these are commercially available [1]. Many mutations remove or create a particular restriction site in the DNA sequence. These mutations can be identified by PCR amplification, incubation of the product with the appropriate enzyme followed by visualisation of the fragments on an agarose gel. 

Restriction endonucleases are found in a wide range of bacterial species. Werner Arber discovered in the early 1960s that their biological function is to recognize and cleave foreign DNA (the DNA of an infecting virus, for example) such DNA is said to be restricted. In the host cell s DNA, the sequence that would be recognized... 

Thousands of restriction endonucleases have been discovered in different bacterial species, and more than 100 different DNA sequences are recognized by one or more of these enzymes. The recognition sequences are usually 4 to 6 bp long and palindromic (see Fig. 8-20). Table 9-2 lists sequences recognized by a few type II restriction endonucleases. In some cases, the interaction between a restriction endonuclease and its target sequence has been elucidated in exquisite molecular detail for example, Figure 9-2 shows the complex of the type II restriction endonuclease EcoRV and its target sequence. 

Arrows indicate the phosphodiester bonds cleaved by each restriction endonuclease, Asterisks indicate bases that are methylated by the corresponding methylase (where known), N denotes any base. Note that the name of each enzyme consists of a three-letter abbreviation (in italics) of the bacterial species from which it is derived, sometimes followed by a strain designation and Roman numerals to distinguish different restriction endonucleases isolated from the same bacterial species, Thus BamHI is the first (I) restriction endonuclease characterized from Bacillus amyloliquefaciens, strain H. 

One of the major obstacles to molecular analysis of genomic DNA is the immense size of the molecules involved. The discovery of a special group of bacterial enzymes, called restriction endonucleases (restriction enzymes), which cleave double-stranded DNA into smaller, more manageable fragments, has opened the way for DNA analysis. Because each enzyme cleaves DNA at a specific nucleotide sequence, restriction enzymes are used experimentally to obtain precisely defined DNA segments called restriction fragments. 

A vector is a molecule of DNA to which the fragment of DNA to be cloned is joined. Essential properties of a vector include 1) it must be capable of autonomous replication within a host cell, 2) it must contain at least one specific nucleotide sequence recognized by a restriction endonuclease, and 3) it must carry at least one gene that confers the ability to select for the vector, such as an antibiotic resistance gene. Commonly used vectors include plasmids and bacterial and animal viruses. 

Let us now consider how knowledge of bacterial sex factors and of phage K permitted the mapping of bacterial chromosomes. Together with the use of restriction endonucleases these techniques gave us the first precise physical maps of bacterial chromosomes and pointed the way toward the determination of complete genome sequences. 

Bacterial cells produce many enzymes that act to degrade various forms of DNA. Of special interest are the restriction endonucleases, enzymes that recognize specific base sequences in double-stranded DNA and catalyze... 

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