DNA polymerase alpha also known as ''Pol α'' 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 ...

complex found in

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

s that is involved in initiation of

DNA replication In molecular biology, DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. DNA replication occurs in all living organisms acting as the most essential part for biological inheritanc ...

. The DNA polymerase alpha complex consists of 4 subunits:

POLA1 DNA polymerase alpha catalytic subunit is an enzyme that in humans is encoded by the ''POLA1'' gene. Function This gene encodes the p180 catalytic subunit of DNA polymerase α-primase. Pol α has limited processivity and lacks 3′ exonucle ...

POLA2 DNA polymerase alpha subunit 2 is an enzyme that in humans is encoded by the ''POLA2'' gene. Interactions POLA2 has been shown to interact with PARP1. See also * DNA Polymerase * DNA polymerase alpha DNA polymerase alpha also known as ''Pol � ...

PRIM1 DNA primase small subunit is an enzyme that in humans is encoded by the ''PRIM1'' gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' o ...

, and

PRIM2 DNA primase large subunit is an enzyme that in humans is encoded by the ''PRIM2'' gene. The replication of DNA in eukaryotic cells is carried out by a complex chromosomal replication apparatus, in which DNA polymerase alpha and primase are two ke ...

. Pol α has limited

processivity In molecular biology and biochemistry, processivity is an enzyme's ability to catalyze "consecutive reactions without releasing its substrate". For example, processivity is the average number of nucleotides added by a polymerase enzyme, such as ...

and lacks 3′

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 ...

activity for proofreading errors. Thus it is not well suited to efficiently and accurately copy long templates (unlike Pol

Delta Delta commonly refers to: * Delta (letter) (Δ or δ), a letter of the Greek alphabet * River delta, at a river mouth * D (NATO phonetic alphabet: "Delta") * Delta Air Lines, US * Delta variant of SARS-CoV-2 that causes COVID-19 Delta may also re ...

and Epsilon). Instead it plays a more limited role in replication. Pol α is responsible for the initiation of DNA replication at origins of replication (on both the leading and lagging strands) and during synthesis of

Okazaki fragment Okazaki fragments are short sequences of DNA nucleotides (approximately 150 to 200 base pairs long in eukaryotes) which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA ...

s on the lagging strand. The Pol α complex (pol α-DNA primase complex) consists of four subunits: the catalytic subunit POLA1, the regulatory subunit

, and the small and the large primase subunits PRIM1 and PRIM2 respectively. Once primase has created the RNA primer, Pol α starts replication elongating the primer with ~20 nucleotides.

Structure

DNA polymerase alpha, like

DNA primase DNA primase is an enzyme involved in the replication of DNA and is a type of RNA polymerase. Primase catalyzes the synthesis of a short RNA (or DNA in some living organisms) segment called a primer complementary to a ssDNA (single-strande ...

, contains iron-sulfur clusters, that are critical in

electron transport An electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples thi ...

that uses DNA itself to transfer electrons at very high speeds; this process is involved in detecting DNA damage, and may also be involved in a feedback between the primase complex and the DNA polymerase alpha.

References

External links

* EC 2.7.7 DNA replication DNA-binding proteins {{2.7-enzyme-stub