Everything about Taq Polymerase totally explained
Taq polymerase is a thermostable
DNA polymerase named after the
thermophilic bacterium
Thermus aquaticus from which it was originally isolated. It is often abbreviated to "
Taq Pol" (or simply "
Taq"), and is frequently used in
polymerase chain reaction (PCR), methods for greatly amplifying short segments of
DNA.
T. aquaticus is a
bacterium that lives in
hot springs and
hydrothermal vents, and Taq polymerase was identified. Therefore it replaced the DNA polymerase from
E.coli originally used in PCR . Taq's temperature optimum for activity is 75-80°C, with a
halflife of 9 minutes at 97.5°C, and can replicate a 1000
base pair strand of DNA in less than 10 seconds at 72°C.
One of Taq's drawbacks is its relatively low replication
fidelity. It lacks a
3' to
5' exonuclease proofreading activity. Some thermostable DNA polymerases, such as
Pfu DNA polymerase, have been isolated from other thermophilic bacteria possessing a proofreading activity, and are being used instead of (or in combination with) Taq for high-fidelity amplification.
Taq makes DNA products that have A (
Adenine) overhangs at their 3' ends. This may be useful in
TA Cloning, whereby a
cloning vector (such as a
plasmid) is used which has a T (
Thymine) 3' overhang, which complements with the A overhang of the PCR product, thus enabling
ligation of the PCR product into the plasmid vector.
Taq polymerase in PCR
In the early 1980s
Kary Mullis was working at
Cetus Corporation on the application of synthetic DNAs to
biotechnology. He was familiar with the use of DNA
oligonucleotides as probes for binding to target DNA strands, as well as their use as
primers for
DNA sequencing and
cDNA synthesis. In 1983, he began using two primers, one to
hybridize to each strand of a target DNA, and adding
DNA polymerase to the reaction. This led to exponential
DNA replication, greatly amplifying the amounts of DNA between the primers. In 1989
Science Magazine named Taq polymerase its first "Molecule of the Year". Kary Mullis received the
Nobel Prize in 1993, the only one awarded for research performed at a
biotechnology company. By the early 1990s the PCR technique with Taq polymerase was being used in many areas, including basic molecular biology research,
clinical testing, and
forensics. It also began to find a pressing application in direct detection of the
HIV virus in
AIDS.
Further Information
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