In biochemistry, a polymerase is an enzyme (EC 2.7.7.6/7/19/48/49) that synthesizes long chains of or . DNA polymerase and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by copying a DNA template strand using Base pair interactions or RNA by half ladder replication.
A DNA polymerase from the thermophile bacterium, Thermus aquaticus ( Taq) (PDB 1BGX, EC 2.7.7.7) is used in the polymerase chain reaction, an important technique of molecular biology.
A polymerase may be template-dependent or template-independent. Poly-A-polymerase is an example of template independent polymerase. Terminal deoxynucleotidyl transferase also known to have template independent and template dependent activities.
By function
| + Classes of Template dependent polymerase
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!DNA-polymerase
!RNA-polymerase |
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DNA polymerase (DNA-directed DNA polymerase, DdDP)
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Family A: DNA polymerase I; Pol POLG, POLQ, ν
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Family B: DNA polymerase II; Pol α, δ, ε, ζ
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Family C: DNA polymerase III holoenzyme
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Family X: Pol β, λ, μ
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Terminal deoxynucleotidyl transferase (TDT), which lends diversity to antibody heavy chains.
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Family Y: DNA polymerase IV (DinB) and DNA polymerase V (UmuD'2C) - SOS response repair polymerases; Pol η, POLI, POLK
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Reverse transcriptase (RT; RNA-directed DNA polymerase; RdDP)
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DNA-directed RNA polymerase (DdRP, RNAP)
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Multi-subunit (msDdRP): RNA polymerase I, RNA polymerase II, RNA polymerase III
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Single-subunit (ssDdRP): T7 RNA polymerase, POLRMT
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Primase, PrimPol
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RNA replicase (RNA-directed RNA polymerase, RdRP)
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Viral (single-subunit)
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Eukaryotic cellular (cRdRP; dual-subunit)
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Template-less RNA elongation
By structure
Polymerases are generally split into two superfamilies, the "right hand" fold () and the "double psi
beta barrel" (often simply "double-barrel") fold. The former is seen in almost all DNA polymerases and almost all viral single-subunit polymerases; they are marked by a conserved "palm" domain.
The latter is seen in all multi-subunit RNA polymerases, in cRdRP, and in "family D" DNA polymerases found in archaea.
The "X" family represented by DNA polymerase beta has only a vague "palm" shape, and is sometimes considered a different superfamily ().
Primases generally don't fall into either category. Bacterial primases usually have the Toprim domain, and are related to and mitochondrial helicase twinkle.
See also
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Central dogma of molecular biology
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Exonuclease
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Ligase
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Nuclease
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PCR
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PARP
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Reverse transcription polymerase chain reaction
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RNA ligase (ATP)
External links
