Polymerase chain reaction , catalytic

While many diseases have long been known to result from alterations in an individual s DNA, tools for the detection of genetic mutations have only recently become widely available. These techniques rely upon the catalytic efficiency and specificity of enzyme catalysts. For example, the polymerase chain reaction (PCR) relies upon the ability of enzymes to serve as catalytic amplifiers to analyze the DNA present in biologic and forensic samples. In the PCR technique, a thermostable DNA polymerase, directed by appropriate oligonucleotide primers, produces thousands of copies of a sample of DNA that was present initially at levels too low for direct detection. 

Other Class A polymerases. The Thermus aquati-cus (Taq) polymerase is best known for its widespread use in the polymerase chain reaction (PCR Fig. 5-47). Like E. coli I the enzyme is a large multidomain protein. The structure of the catalytic domains of the two enzymes are nearly identical, but the Taq polymerase has poor 3 -5 editing activity.276 The enzyme has been carefully engineered to improve its characteristics for use in the PCR reaction.277... 

The demonstration that the polymerase chain reaction can be carried out in liposomes [50] is important because it demonstrates that liposomes can resist the required temperature changes. In the light of the lipid world model it is useful to ask what catalytic functions Luisi s structures show behind direct auto catalysis. Binding of peptides to and polymerisation of amino acids in liposomes was demonstrated in various systems [51]. We are not aware of a similar effect on nucleic acid synthesis. 

For the combinatorial selection of RNA (or DNA)-transition-metal catalysts, further elements have to be developed and integrated into the scheme (Figure 18.3). In addition to a tethered substrate, a site-specifically attached transition metal ligand needs to be present in each molecule of the hbrary. After loading with the metal, it should allow formation of the catalytically active species, preferably with the reactant tethered to the same RNA molecule. The other reactant carries a purification tag, allowing the selective isolation of only those species in which a reaction had taken place. A further nontrivial requirement is that the attachment of the metal-hgand complex to DNA or RNA does not interfere with the enzymatic copying steps (transcription, reverse transcription (RT), polymerase chain reaction (PCR)). 

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