Restriction endonucleases, function

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... 

A multitude of nucleases cleave DNA, single- or double-stranded. They range from the pancreatic digestive enzyme DNase I through specialized nucleases that function during DNA repair and the hundreds of restriction endonucleases that have become so valuable in modern laboratory work. Some nucleases leave a 3 -phosphate ester at a cut end in a DNA chain, while others leave a 5 -phosphate end.824 Many nucleases are dealt with in later chapters. Only a few will be mentioned here. 

If recombinant DNA and related techniques in molecular biology are to be applied meaningfully to cestodes, functional nucleic acids have to be prepared such that the DNA can be cleaved by restriction endonuclease enzymes (which digest the double-stranded DNA at highly specific sites, each recognizing a precise nucleotide sequence) and the RNA can be used to... 

Fig. 5. Schematic of the construction and function of chimeric restriction endonucleases (Chandrasegaran and Smith, 1999). (a) The type IIS restriction enzyme Fokl has a nonspecific endonuclease domain (FN) and a DNA-binding domain. Swapping Fokl s DNA binding-domain for that of another DNA binding-domain results in a chimeric restriction enzyme with new specificity. The flexibility resulting from less intimate contact between the Fn domain and its new DNA-binding domain translates into DNA cleavage at several locations near the binding site, (b) The modular nature and tunable specificity of zinc...

Fundamental knowledge of the structure, function and mechanism of DNA-modifying enzymes has been important not only in understanding how these enzymes perform a myriad of chemical reactions Ml vZvo but also for the development of the field of recombinant DNA technology. The functions of the major groups of enzymes in deoxyribonucleic acid synthesis, hydrolysis and modification are reviewed, as well as some structural and mechanistic aspects of the restriction endonucleases, ligases and polymerases. 

Type II restriction endonucleases recognize specific base sequences in double-stranded DNA, and cleave both strands of the duplex. More than 600 restriction endonucleases have been reported in the literature. Some 121 restriction endonucleases are listed in Current Protocols in Molecular Biology as commercially available ( 3). Table II, adapted from the 1988 Sigma Chemical Company Catalog, lists 35 of the endonucleases available from that source. Endonucleases are found in many bacteria where their function is to hydrolyze foreign DNA introduced by phage infection, conjugation or transformation. The first restriction endonucleases were discovered and isolated in 1968 (4,5). 

The extension of recognition sequences of type II restriction endonucleases also turned out to be a more than difficult job. The function of the different contacts within the protein DNA interface is still poorly understood, as is the mechanism of how... 

Restriaion enzymes are a revolutionary class of proteins discovered in prokaryotic organisms in the early 1970s (1-5). These enzymes reproducibly cut within double-stranded DNA molecules at specific nucleotide recognition sequences, termed restriction sites, hence their more specific appellation as restriction endonucleases (Fig. 1). Their complete range of enzymatic functions is not fully... 

R. A. and Matthews, B.W., Type II restriction endonucleases structural, functional, and evolutionary relationships, Curr. Opin. Chem. Biol. 3, 578-583, 1999 Akar, A., Orkunoglu, F.E., Ozata, M., Sengul, A., and Gur, A.R., Lack of association between vitamin D receptor Fokl polymorphism and alopecia areata, Eur. J. Dermatol. 14, 156-158, 2004 Guy, M., Lowe, L.C., Bretherton-Watt, D. et al., Vitamin D receptor gene polymorphisms and breast cancer risk, Clin. Cancer Res. 10, 5472-5481, 2004 Claassen, M., Nouwen, J., Fang, Y. et al., Staphylococcus aureus nasal carriage is not associated with known polymorphism in the Vitamin D receptor gene, FEMS Immunol. Med. Microbiol. 43,173-176, 2005 Bolu,... 

Restriction endonucleases as well as many other enzymes that act on phosphate-containing substrates require Mg2+ or some other similar divalent cation for activity. What is the function of this metal ... 

Methyl groups can be added to bases in DNA. Except for some yeasts and insects, all DNA contains methylated bases. The attachment of methyl groups to bases at specific sequences in DNA acts to regulate the functions of DNA. One function of site-specific methylation in prokaryotes is to protect endogenous bacterial DNA from digestion by restriction endonucleases produced by the bacteria. 

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