{"history":[],"article":{"id":"b275ea59-6da6-4f6f-80d5-1d8d8bd819b3","title":"DNA polymerase III holoenzyme","slug":"dna-polymerase-iii-holoenzyme","content":":::summary\n:::\n\n# \n**DNA polymerase III holo[enzyme](https://bliptext.com/articles/enzyme)** is the primary [enzyme](https://bliptext.com/articles/enzyme) complex involved in [prokaryotic](https://bliptext.com/articles/prokaryotic) [DNA replication](https://bliptext.com/articles/dna-replication).\nIt was discovered by [Thomas Kornberg](https://bliptext.com/articles/thomas-b-kornberg) (son of [Arthur Kornberg](https://bliptext.com/articles/arthur-kornberg)) and [Malcolm Gefter](https://bliptext.com/articles/malcolm-gefter) in 1970.\nThe complex has high processivity (i.e. the number of [nucleotides](https://bliptext.com/articles/nucleotide) added per binding event) and, specifically referring to the replication of the [E.coli](https://bliptext.com/articles/escherichia-coli) [genome](https://bliptext.com/articles/genome), works in conjunction with four other DNA polymerases ([Pol I](https://bliptext.com/articles/pol-i), [Pol I](https://bliptext.com/articles/pol-i)I, [Pol I](https://bliptext.com/articles/pol-i)V, and [Pol V](https://bliptext.com/articles/pol-v)).\nBeing the primary [holoenzyme](https://bliptext.com/articles/[holoenzyme](https://bliptext.com/articles/holoenzyme)) involved in replication activity, the DNA Pol III [holoenzyme](https://bliptext.com/articles/[holoenzyme](https://bliptext.com/articles/holoenzyme)) also has proofreading capabilities that corrects replication mistakes by means of [exonuclease](https://bliptext.com/articles/exonuclease) activity reading 3'→5' and synthesizing 5'→3'.\nDNA Pol III is a component of the [replisome](https://bliptext.com/articles/replisome), which is located at the replication fork.\n# [Schematic picture of DNA polymerase III* (with subunits). This is the old textbook \"trombone model\" with two units of Pol III. | upload.wikimedia.org/wikipedia/commons/a/a2/DNA///polymerase///III///%28with///subunits%29.jpg]\n\n# Components\nThe replisome is composed of the following:\n\n# Activity\nDNA polymerase III synthesizes base pairs at a rate of around 1000 nucleotides per second.\nDNA Pol III activity begins after strand separation at the origin of replication.\nBecause DNA synthesis cannot start de novo, an [RNA primer](https://bliptext.com/articles/rna-primer), complementary to part of the single-stranded DNA, is synthesized by [primase](https://bliptext.com/articles/primase) (an [RNA polymerase](https://bliptext.com/articles/rna-polymerase)):\n(\"!\" for [RNA](https://bliptext.com/articles/rna), '\"$\" for [DNA](https://bliptext.com/articles/dna), \"*\" for [polymerase](https://bliptext.com/articles/polymerase))\n> * * * * ! ! ! ! _ _ _ _ _ _ _ _ | [RNA](https://bliptext.com/articles/rna) | <--[ribose](https://bliptext.com/articles/ribose) (sugar)-phosphate backbone\nG U A U | [Pol](https://bliptext.com/articles/polymerase) | <--[RNA primer](https://bliptext.com/articles/rna-primer)\n* * * * |_ _ _ _| <--hydrogen bonding\nC A T A G C A T C C <--[template](https://bliptext.com/articles/dna) ss[DNA](https://bliptext.com/articles/dna) (single-stranded [DNA](https://bliptext.com/articles/dna))\n_ _ _ _ _ _ _ _ _ _ <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\n$ $ $ $ $ $ $ $ $ $\n\n## Addition onto 3'OH\nAs replication progresses and the [replisome](https://bliptext.com/articles/replisome) moves forward, DNA polymerase III arrives at the RNA primer and begins replicating the DNA, adding onto the 3'OH of the primer:\n* * * * ! ! ! ! _ _ _ _ _ _ _ _ | [DNA](https://bliptext.com/articles/dna) | <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\nG U A U | [Pol](https://bliptext.com/articles/polymerase) | <--[RNA primer](https://bliptext.com/articles/rna-primer)\n* * * * |_III_ _| <--hydrogen bonding\nC A T A G C A T C C <--[template](https://bliptext.com/articles/dna) ss[DNA](https://bliptext.com/articles/dna) (single-stranded [DNA](https://bliptext.com/articles/dna))\n_ _ _ _ _ _ _ _ _ _ <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\n$ $ $ $ $ $ $ $ $ $\n\n## Synthesis of DNA\nDNA polymerase III will then synthesize a continuous or discontinuous strand of DNA, depending if this is occurring on the leading or lagging strand ([Okazaki fragment](https://bliptext.com/articles/okazaki-fragment)) of the DNA.\nDNA polymerase III has a high processivity and therefore, synthesizes DNA very quickly.\nThis high processivity is due in part to the β-clamps that \"hold\" onto the DNA strands.\n---> * * * * ! ! ! ! $ $ $ $ $ $ _ _ _ _ _ _ _ _ _ _ _ _ _ _| [DNA](https://bliptext.com/articles/dna) | <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\nG U A U C G T A G G| [Pol](https://bliptext.com/articles/polymerase) | <--[RNA primer](https://bliptext.com/articles/rna-primer)\n* * * * * * * * * *|_III_ _| <--hydrogen bonding\nC A T A G C A T C C <--[template](https://bliptext.com/articles/dna) ss[DNA](https://bliptext.com/articles/dna) (single-stranded [DNA](https://bliptext.com/articles/dna))\n_ _ _ _ _ _ _ _ _ _ <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\n$ $ $ $ $ $ $ $ $ $\n\n## Removal of primer\nAfter replication of the desired region, the RNA primer is removed by [DNA polymerase I](https://bliptext.com/articles/dna-polymerase-i) via the process of [nick translation](https://bliptext.com/articles/nick-translation).\nThe removal of the RNA primer allows [DNA ligase](https://bliptext.com/articles/dna-ligase) to ligate the DNA-DNA nick between the new fragment and the previous strand.\nDNA polymerase I & III, along with many other enzymes are all required for the high fidelity, high-processivity of DNA replication.","current_revision":null,"created_by":"kACnuQmH5k9Nr5VNVEpVeg7XpvUmMctD","created_at":"2025-01-25T19:53:34.360Z","updated_at":"2025-01-25T19:53:34.360Z","search_vector":"'dna':1 'holoenzym':4 'iii':3 'polymeras':2","search_content":" \n \n\n# \n**DNA polymerase III holo[enzyme](https://bliptext.com/articles/enzyme)** is the primary [enzyme](https://bliptext.com/articles/enzyme) complex involved in [prokaryotic](https://bliptext.com/articles/prokaryotic) [DNA replication](https://bliptext.com/articles/dna-replication).\nIt was discovered by [Thomas Kornberg](https://bliptext.com/articles/thomas-b-kornberg) (son of [Arthur Kornberg](https://bliptext.com/articles/arthur-kornberg)) and [Malcolm Gefter](https://bliptext.com/articles/malcolm-gefter) in 1970.\nThe complex has high processivity (i.e. the number of [nucleotides](https://bliptext.com/articles/nucleotide) added per binding event) and, specifically referring to the replication of the [E.coli](https://bliptext.com/articles/escherichia-coli) [genome](https://bliptext.com/articles/genome), works in conjunction with four other DNA polymerases ([Pol I](https://bliptext.com/articles/pol-i), [Pol I](https://bliptext.com/articles/pol-i)I, [Pol I](https://bliptext.com/articles/pol-i)V, and [Pol V](https://bliptext.com/articles/pol-v)).\nBeing the primary [[holoenzyme](https://bliptext.com/articles/holoenzyme)](https://bliptext.com/articles/[holoenzyme](https://bliptext.com/articles/holoenzyme)) involved in replication activity, the DNA Pol III [[holoenzyme](https://bliptext.com/articles/holoenzyme)](https://bliptext.com/articles/[holoenzyme](https://bliptext.com/articles/holoenzyme)) also has proofreading capabilities that corrects replication mistakes by means of [exonuclease](https://bliptext.com/articles/exonuclease) activity reading 3'→5' and synthesizing 5'→3'.\nDNA Pol III is a component of the [replisome](https://bliptext.com/articles/replisome), which is located at the replication fork.\n# [Schematic picture of DNA polymerase III* (with subunits). This is the old textbook \"trombone model\" with two units of Pol III. | upload.wikimedia.org/wikipedia/commons/a/a2/DNA///polymerase///III///%28with///subunits%29.jpg]\n\n# Components\nThe replisome is composed of the following:\n\n# Activity\nDNA polymerase III synthesizes base pairs at a rate of around 1000 nucleotides per second.\nDNA Pol III activity begins after strand separation at the origin of replication.\nBecause DNA synthesis cannot start de novo, an [RNA primer](https://bliptext.com/articles/rna-primer), complementary to part of the single-stranded DNA, is synthesized by [primase](https://bliptext.com/articles/primase) (an [RNA polymerase](https://bliptext.com/articles/rna-polymerase)):\n(\"!\" for [RNA](https://bliptext.com/articles/rna), '\"$\" for [DNA](https://bliptext.com/articles/dna), \"*\" for [polymerase](https://bliptext.com/articles/polymerase))\n> * * * * ! ! ! ! _ _ _ _ _ _ _ _ | [RNA](https://bliptext.com/articles/rna) | * * * * ! ! ! ! $ $ $ $ $ $ _ _ _ _ _ _ _ _ _ _ _ _ _ _| [DNA](https://bliptext.com/articles/dna) | <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\nG U A U C G T A G G| [Pol](https://bliptext.com/articles/polymerase) | <--[RNA primer](https://bliptext.com/articles/rna-primer)\n* * * * * * * * * *|_III_ _| <--hydrogen bonding\nC A T A G C A T C C <--[template](https://bliptext.com/articles/dna) ss[[DNA](https://bliptext.com/articles/dna)](https://bliptext.com/articles/dna) (single-stranded [[DNA](https://bliptext.com/articles/dna)](https://bliptext.com/articles/dna))\n_ _ _ _ _ _ _ _ _ _ <--[deoxyribose](https://bliptext.com/articles/deoxyribose) (sugar)-phosphate backbone\n$ $ $ $ $ $ $ $ $ $\n\n## Removal of primer\nAfter replication of the desired region, the RNA primer is removed by [DNA polymerase I](https://bliptext.com/articles/dna-polymerase-i) via the process of [nick translation](https://bliptext.com/articles/nick-translation).\nThe removal of the RNA primer allows [DNA ligase](https://bliptext.com/articles/dna-ligase) to ligate the DNA-DNA nick between the new fragment and the previous strand.\nDNA polymerase I & III, along with many other enzymes are all required for the high fidelity, high-processivity of DNA replication.","revisionCount":0},"hasMore":false,"nextCursor":null}

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