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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 DNA polymerase, per association event with the template strand. Because the binding of the polymerase to the template is the rate-limiting step in DNA synthesis, the overall rate of DNA replication during S phase of the cell cycle is dependent on the processivity of the DNA polymerases performing the replication. DNA clamp proteins are integral components of the DNA replication machinery and serve to increase the processivity of their associated polymerases. Some polymerases add over 50,000 nucleotides to a growing DNA strand before dissociating from the template strand, giving a replication rate of up to 1,000 nucleotides per second. DNA binding interactions Polymerases interact with the phosphate backbone and the minor groove of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 two identical DNA duplexes from a single original DNA duplex. During this process, DNA polymerase "reads" the existing DNA strands to create two new strands that match the existing ones. These enzymes catalysis, catalyze the chemical reaction : deoxynucleoside triphosphate + DNAn pyrophosphate + DNAn+1. DNA polymerase adds nucleotides to the Directionality (molecular biology), three prime (3')-end of a DNA strand, one nucleotide at a time. Every time a Cell division, cell divides, DNA polymerases are required to duplicate the cell's DNA, so that a copy of the original DNA molecule can be passed to each daughter cell. In this way, genetic information is passed down from generation to generation. Before replication can take place, an enzy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 life, living organisms, acting as the most essential part of heredity, biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential. DNA is made up of a nucleic acid double helix, double helix of two Complementary DNA, complementary DNA strand, strands. DNA is often called double helix. The double helix describes the appearance of a double-stranded DNA which is composed of two linear strands that run opposite to each other and twist together. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Replication Fork
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 of biological inheritance. This is essential for cell division during growth and repair of damaged tissues, while it also ensures that each of the new cells receives its own copy of the DNA. The cell possesses the distinctive property of division, which makes replication of DNA essential. DNA is made up of a double helix of two complementary strands. DNA is often called double helix. The double helix describes the appearance of a double-stranded DNA which is composed of two linear strands that run opposite to each other and twist together. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. As a result, th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pol III
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 nucleotides added per binding event) and, specifically referring to the replication of the '' E.coli'' genome, works in conjunction with four other DNA polymerases ( Pol I, Pol II, Pol IV, and Pol V). Being the primary holoenzyme involved in replication activity, the DNA Pol III holoenzyme also has proofreading capabilities that corrects replication mistakes by means of exonuclease activity reading 3'→5' and synthesizing 5'→3'. DNA Pol III is a component of the replisome, which is located at the replication fork. Components The replisome is composed of the following: *2 DNA Pol III enzymes, each comprising α, ε and θ subunits. (It has been proven that there is a third copy of Pol III at the replisome.) **the α subunit (enc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Polymerase Alpha
DNA polymerase alpha also known as ''Pol α'' is an enzyme complex found in eukaryotes that is involved in initiation of DNA replication. The DNA polymerase alpha complex consists of 4 subunits: POLA1, POLA2, PRIM1, and PRIM2. Pol α has limited processivity and lacks 3′ exonuclease activity for proofreading errors. Thus it is not well suited to efficiently and accurately copy long templates (unlike Pol Delta 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 fragments on the lagging strand. The Pol α complex (pol α-DNA primase complex) consists of four subunits: the catalytic subunit POLA1, the regulatory subunit POLA2, 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Polymerase Delta
DNA polymerase delta (DNA Pol δ) is an enzyme complex found in eukaryotes that is involved in DNA replication and repair. The DNA polymerase delta complex consists of 4 subunits: POLD1, POLD2, POLD3, and POLD4. DNA Pol δ is an enzyme used for both leading and lagging strand synthesis. It exhibits increased processivity when interacting with the proliferating cell nuclear antigen (PCNA). As well, the multisubunit protein replication factor C The replication factor C, or RFC, is a five-subunit protein complex that is required for DNA replication. The subunits of this heteropentamer are named Rfc1, Rfc2, Rfc3, Rfc4, and Rfc5 in ''Saccharomyces cerevisiae''. RFC is used in eukaryo ..., through its role as the clamp loader for PCNA (which involves catalysing the loading of PCNA on to DNA) is important for DNA Pol δ function. References External links * EC 2.7.7 DNA replication DNA repair DNA-binding proteins {{2.7-enzyme-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Prokaryote
A prokaryote (; less commonly spelled procaryote) is a unicellular organism, single-celled organism whose cell (biology), cell lacks a cell nucleus, nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Greek (), meaning 'before', and (), meaning 'nut' or 'kernel'. In the earlier two-empire system arising from the work of Édouard Chatton, prokaryotes were classified within the empire Prokaryota. However, in the three-domain system, based upon molecular phylogenetics, prokaryotes are divided into two domain (biology), domains: Bacteria and Archaea. A third domain, Eukaryote, Eukaryota, consists of organisms with nuclei. Prokaryotes evolution, evolved before eukaryotes, and lack nuclei, mitochondria, and most of the other distinct organelles that characterize the eukaryotic cell. Some unicellular prokaryotes, such as cyanobacteria, form colony (biology), colonies held together by biofilms, and large colonies can create multilayered microbial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
DNA Polymerase Epsilon
DNA polymerase epsilon is a member of the DNA polymerase family of enzymes found in eukaryotes. It is composed of the following four subunits: POLE (central catalytic unit), POLE2 (subunit 2), POLE3 (subunit 3), and POLE4 (subunit 4). Recent evidence suggests that it plays a major role in leading strand DNA synthesis and nucleotide and base excision repair. Research had conducted to study nucleotide excision repair DNA synthesis by DNA polymerase epsilon in the presence of PCNA (proliferating cell nuclear antigen), RFC (replication factor C) and RPA (replication protein A). Either DNA polymerase epsilon or DNA polymerase delta DNA polymerase delta (DNA Pol δ) is an enzyme complex found in eukaryotes that is involved in DNA replication and repair. The DNA polymerase delta complex consists of 4 subunits: POLD1, POLD2, POLD3, and POLD4. DNA Pol δ is an enzyme used f ... along with DNA ligase can be used to repair UV-damaged DNA. However, it is found that DNA polymera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryote
The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms are eukaryotes. They constitute a major group of Outline of life forms, life forms alongside the two groups of prokaryotes: the Bacteria and the Archaea. Eukaryotes represent a small minority of the number of organisms, but given their generally much larger size, their collective global biomass is much larger than that of prokaryotes. The eukaryotes emerged within the archaeal Kingdom (biology), kingdom Asgard (Archaea), Promethearchaeati and its sole phylum Promethearchaeota. This implies that there are only Two-domain system, two domains of life, Bacteria and Archaea, with eukaryotes incorporated among the Archaea. Eukaryotes first emerged during the Paleoproterozoic, likely as Flagellated cell, flagellated cells. The leading evolutiona ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RNA Primer
A primer is a short, single-stranded nucleic acid used by all living organisms in the initiation of DNA synthesis. A synthetic primer is a type of oligo, short for oligonucleotide. DNA polymerases (responsible for DNA replication) are only capable of adding nucleotides to the 3’-end of an existing nucleic acid, requiring a primer be bound to the template before DNA polymerase can begin a complementary strand. DNA polymerase adds nucleotides after binding to the RNA primer and synthesizes the whole strand. Later, the RNA strands must be removed accurately and replaced with DNA nucleotides. This forms a gap region known as a nick that is filled in using a ligase. The removal process of the RNA primer requires several enzymes, such as Fen1, Lig1, and others that work in coordination with DNA polymerase, to ensure the removal of the RNA nucleotides and the addition of DNA nucleotides. Living organisms use solely RNA primers, while laboratory techniques in biochemistry and molecula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 endonuclease, which cleaves phosphodiester bonds in the middle (endo) of a polynucleotide chain. Eukaryotes and prokaryotes have three types of exonucleases involved in the normal turnover of mRNA: 5′ to 3′ exonuclease (Xrn1), which is a dependent decapping protein; 3′ to 5′ exonuclease, an independent protein; and poly(A)-specific 3′ to 5′ exonuclease. In both archaea and eukaryotes, one of the main routes of RNA degradation is performed by the multi-protein exosome complex, which consists largely of 3′ to 5′ exoribonucleases. Significance to polymerase RNA polymerase II is known to be in effect during transcriptional termination; it works with a 5' exonuclease (human gene Xrn2) to degrade the newly formed transcr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pol 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 initially characterized in ''E. coli'' and is ubiquitous in prokaryotes. In ''E. coli'' and many other bacteria, the gene that encodes Pol I is known as ''polA''. The ''E. coli'' Pol I enzyme is composed of 928 amino acids, and is an example of a processive enzyme — it can sequentially catalyze multiple polymerisation steps without releasing the single-stranded template. The physiological function of Pol I is mainly to support repair of damaged DNA, but it also contributes to connecting Okazaki fragments by deleting RNA primers and replacing the ribonucleotides with DNA. Discovery In 1956, Arthur Kornberg and colleagues discovered Pol I by using ''Escherichia coli'' (''E. coli'') extracts to develop a DNA synthesis assay. The scientists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
