DNA Polymerase, Taq - Manual

DNA polymerase I was the first enzyme thought to be involved in DNA synthesis and was the only DNA polymerase to be studied from the late 1950s to the early 1970s (Kornberg et al. 1956, Bessman et al. 1957, Buttin and Kornberg 1966, Englund et al. 1968, Deutsch and Kornberg 1969, Englund et al. 1969, and Kornberg et al. 1974). In 1969, DeLucia and Cairns isolated an E. coli strain with a mutation that affected the DNA polymerase and surprisingly found that the mutant synthesized DNA normally. This discovery casted doubts on the role of DNA polymerase in replication and led groups to search for other replication enzymes.

DNA polymerase II and III of E. coli were soon isolated and characterized (Kornberg and Gefter 1972, and Livingston and Richardson 1975). However, few attempts were made to isolate DNA polymerase from thermophiles (Stenesh and Roe 1972). In 1976, DNA polymerase from the thermophilic bacterium Thermus aquaticus was first isolated and purified, and its remarkable stability at high temperatures was described (Chien et al. 1976).

Soon after its purification, Taq DNA polymerase was found to be highly useful in the polymerase chain reaction (PCR) method of DNA amplification. Compared to E. coli DNA polymerase I, Taq polymerase’s high specificity of primer binding at elevated temperatures was found to give a higher yield of the desired product with less non-specific amplification product (Saiki et al. 1985, Mullis and Faloona 1987, and Lawyer et al. 1989). This feature paved the way for dramatic improvements to the PCR method. Since its optimal temperature is so high, Taq polymerase only needs to be added to a PCR reaction at the beginning, rather than before each round of amplification. 

The crystal structure was determined by Kim et al. in 1995. Recent work with Taq polymerase has included developing inhibitor-resistant mutants of Taq polymerases for use in PCR assays (Baar et al. 2011) and investigating the molecular basis of substrate specificity through thermodynamic and structural studies (Obeid et al. 2010, and Wowor et al. 2010).