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. A ...
(
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 cl ...
s.
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 create ...
and
RNA polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template.
Using the enzyme helicase, RNAP locally opens the ...
are used to assemble
DNA and
RNA
Ribonucleic acid (RNA) is a polymeric molecule essential in various biological roles in coding, decoding, regulation and expression of genes. RNA and deoxyribonucleic acid ( DNA) are nucleic acids. Along with lipids, proteins, and carbohydra ...
molecules, respectively, by copying a DNA template strand using
base-pairing
A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
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 among ...
, ''
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) t ...
, 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 physi ...
.
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 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 create ...
(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 initiall ...
; Pol
γ,
θ,
ν
**Family B:
DNA polymerase II
DNA polymerase II (also known as DNA Pol II or Pol II) is a prokaryotic DNA-Dependent DNA polymerase encoded by the PolB gene.
DNA Polymerase II is an 89.9-kDa protein and is a member of the B family of DNA polymerases. It was originally isolated ...
; 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 of ...
**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' Protein dimer, homodimer and a UmuC monomer, forming the UmuD'2C protein complex. It is part of ...
(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 genomes, ...
(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 euka ...
*DNA-directed
RNA polymerase
In molecular biology, RNA polymerase (abbreviated RNAP or RNApol), or more specifically DNA-directed/dependent RNA polymerase (DdRP), is an enzyme that synthesizes RNA from a DNA template.
Using the enzyme helicase, RNAP locally opens the ...
(DdRP, RNAP)
**Multi-subunit (msDdRP):
RNA polymerase I
RNA polymerase 1 (also known as Pol I) is, in higher eukaryotes, the polymerase that only transcribes ribosomal RNA (but not 5S rRNA, which is synthesized by RNA polymerase III), a type of RNA that accounts for over 50% of the total RNA synthesiz ...
,
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 eukaryoti ...
,
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
DNA polymerase beta, also known as POLB, is an enzyme present in eukaryotes. In humans, it is encoded by the ''POLB'' gene.
Function
In eukaryotic cells, DNA polymerase beta (POLB) performs base excision repair (BER) required for DNA mainten ...
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
topoisomerase
DNA topoisomerases (or topoisomerases) are enzymes that catalyze changes in the topological state of DNA, interconverting relaxed and supercoiled forms, linked (catenated) and unlinked species, and knotted and unknotted DNA. Topological issues i ...
s and mitochondrial helicase
twinkle
Twinkle may refer to:
* Twinkling, the variation of brightness of distant objects
People
* Twinkle (singer) (1948–2015), born Lynn Annette Ripley, English singer-songwriter
* Twinkle Khanna, Indian movie actress
* Twinkle Bajpai, female conte ...
. 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.
See also
*
Central dogma of molecular biology
The central dogma of molecular biology is an explanation of the flow of genetic information within a biological system. It is often stated as "DNA makes RNA, and RNA makes protein", although this is not its original meaning. It was first stated by ...
*
Exonuclease
Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. Its close relative is the ...
*
Ligase
*
Nuclease
A nuclease (also archaically known as nucleodepolymerase or polynucleotidase) is an enzyme capable of cleaving the phosphodiester bonds between nucleotides of nucleic acids. Nucleases variously effect single and double stranded breaks in their ta ...
*
PCR
*
PARP
*
Reverse transcription polymerase chain reaction
Reverse transcription polymerase chain reaction (RT-PCR) is a laboratory technique combining reverse transcription of RNA into DNA (in this context called complementary DNA or cDNA) and amplification of specific DNA targets using polymerase cha ...
*
RNA ligase (ATP)
References
External links
{{Portal bar, Biology, border=no
EC 2.7.7
Enzymes