A polymerase is an

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

( EC 2.7.7.6/7/19/48/49) that synthesizes long chains of

polymer A polymer (; Greek '' poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

s or

nucleic acid Nucleic acids are biopolymers, macromolecules, essential to all known forms of life. They are composed of nucleotides, which are the monomers made of three components: a 5-carbon sugar, a phosphate group and a nitrogenous base. The two main ...

DNA polymerase A DNA polymerase is a member of a family of enzymes that catalyze the synthesis of DNA molecules from nucleoside triphosphates, the molecular precursors of DNA. These enzymes are essential for DNA replication and usually work in groups to crea ...

and RNA polymerase are used to assemble DNA and RNA molecules, respectively, by copying a DNA template strand using base-pairing interactions or RNA by half ladder replication. A DNA polymerase from the thermophilic

bacterium Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...

, '' Thermus aquaticus'' (''Taq'') ( PDBbr>1BGX
EC 2.7.7.7) is used in the

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to rapidly make millions to billions of copies (complete or partial) of a specific DNA sample, allowing scientists to take a very small sample of DNA and amplify it (or a part of it) ...

, an important technique of

molecular biology Molecular biology is the branch of biology that seeks to understand the molecular basis of biological activity in and between cells, including biomolecular synthesis, modification, mechanisms, and interactions. The study of chemical and phys ...

. 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.

Types

By function

(DNA-directed DNA polymerase, DdDP) **Family A:

DNA polymerase I DNA polymerase I (or Pol I) is an enzyme that participates in the process of prokaryotic DNA replication. Discovered by Arthur Kornberg in 1956, it was the first known DNA polymerase (and the first known of any kind of polymerase). It was initia ...

; Pol γ, θ, ν **Family B: DNA polymerase II; Pol α, δ, ε, ζ **Family C:

DNA polymerase III holoenzyme DNA polymerase III holoenzyme is the primary enzyme complex involved in prokaryotic DNA replication. It was discovered by Thomas Kornberg (son of Arthur Kornberg) and Malcolm Gefter in 1970. The complex has high processivity (i.e. the number ...

**Family X: Pol β, λ, μ *** Terminal deoxynucleotidyl transferase (TDT), which lends diversity to antibody heavy chains. **Family Y:

DNA polymerase IV DNA polymerase IV is a prokaryotic polymerase that is involved in mutagenesis and is encoded by the ''dinB'' gene. It exhibits no 3′→5′ exonuclease (proofreading) activity and hence is error prone. In ''E. coli'', DNA polymerase IV (Pol 4) ...

(DinB) and

DNA polymerase V DNA Polymerase V (Pol V) is a polymerase enzyme involved in DNA repair mechanisms in bacteria, such as ''Escherichia coli''. It is composed of a UmuD' homodimer and a UmuC monomer, forming the UmuD'2C protein complex. It is part of the Y-famil ...

(UmuD'2C) -

SOS is a Morse code distress signal (), used internationally, that was originally established for maritime use. In formal notation is written with an overscore line, to indicate that the Morse code equivalents for the individual letters of "SOS" ...

repair polymerases; Pol η, ι, κ *

Reverse transcriptase A reverse transcriptase (RT) is an enzyme used to generate complementary DNA (cDNA) from an RNA template, a process termed reverse transcription. Reverse transcriptases are used by viruses such as HIV and hepatitis B to replicate their genom ...

(RT; RNA-directed DNA polymerase; RdDP) **

Telomerase Telomerase, also called terminal transferase, is a ribonucleoprotein that adds a species-dependent telomere repeat sequence to the 3' end of telomeres. A telomere is a region of repetitive sequences at each end of the chromosomes of most euk ...

*DNA-directed RNA polymerase (DdRP, RNAP) **Multi-subunit (msDdRP): RNA polymerase I,

RNA polymerase II RNA polymerase II (RNAP II and Pol II) is a multiprotein complex that transcribes DNA into precursors of messenger RNA (mRNA) and most small nuclear RNA (snRNA) and microRNA. It is one of the three RNAP enzymes found in the nucleus of euka ...

, RNA polymerase III **Single-subunit (ssDdRP): T7 RNA polymerase, POLRMT ** Primase, PrimPol * RNA replicase (RNA-directed RNA polymerase, RdRP) **Viral (single-subunit) **Eukaryotic cellular (cRdRP; dual-subunit) *Template-less RNA elongation **

Polyadenylation Polyadenylation is the addition of a poly(A) tail to an RNA transcript, typically a messenger RNA (mRNA). The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In euk ...

: PAP, PNPase

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 topoisomerases and mitochondrial helicase twinkle. Archae and eukaryotic primases form an unrelated AEP family, possibly related to the polymerase palm. Both families nevertheless associate to the same set of helicases. File:WikiHandDNAPolII.png, Right hand structure of Bacteriophage RB69, a family B DdRP.

References

External links

{{Portal bar, Biology, border=no EC 2.7.7 Enzymes

Types

By function

By structure

See also

References

External links