I-RNA polymerase iyi-enzyme ebalulekile ekulotshweni kwe-DNA ku-RNA. Inesibopho sokuhlanganisa ama-molecule e-RNA asuka kusifanekiso se-DNA. Isakhiwo se-RNA polymerase ilondolozwe kakhulu kuzo zonke izinto eziphilayo, kusukela kumagciwane kuya kubantu.
Kuma-prokaryotes, njengama-bacterium, i-RNA polymerase yakhiwa amayunithi amaningana asebenza ndawonye ukuze abone abagqugquzeli be-DNA futhi aqale ukuloba. Ku-eukaryote, i-RNA polymerase iyinkimbinkimbi kakhulu, ihlukaniswa yaba izinhlobo eziningana ezibhala izinhlobo ezahlukene ze-RNA, njenge- messenger RNA, i-ribosomal RNA, kanye ne-RNA yokudlulisa.
Ngaphezu komsebenzi wayo oyinhloko ekulotshweni kwe-DNA, i-RNA polymerase nayo idlala indima ebalulekile ekulawuleni ukubonakaliswa kofuzo, ukuphendula kumasiginali angaphakathi nangaphandle kanye nokwenza kusebenze noma kungasebenzi ukulotshwa kofuzo oluthile. Ngamafuphi, i-RNA polymerase iyi-enzyme eyisisekelo yokuhlanganiswa kwe-RNA kuzo zonke izinto eziphilayo, edlala indima ebalulekile ekuvezeni izakhi zofuzo nokusebenza kwamangqamuzana.
Ukulawulwa komsebenzi we-RNA polymerase: izindlela zokulawula ngaphakathi kweseli.
I-RNA polymerase iyi-enzyme ebalulekile ekuhlanganiseni kwe-RNA kuzo zonke izinto eziphilayo. Idlala indima ebalulekile ekulotshweni kwe-DNA ibe yi-RNA yesithunywa, yona ihunyushwa ibe amaprotheni. Ukulawulwa komsebenzi we-RNA polymerase kubalulekile ekulawuleni ukubonakaliswa kofuzo, ngenxa yalokho, i-homeostasis yeselula.
Kunezindlela eziningana zokulawula umsebenzi we-RNA polymerase, kokubili kuma-prokaryotes nama-eukaryotes. Ku-prokaryotes, ukulawulwa kwenzeka ngokuyinhloko ngamaprotheni abizwa ngokuthi ama-sigma factor, abophezela ku-RNA polymerase futhi aqondise umsebenzi wawo kubagqugquzeli abathile. Ngaphezu kwalokho, ukuboshwa kwe-activator noma amaprotheni okucindezela ku-DNA kungashintsha ukusebenzisana kwe-RNA polymerase nomgqugquzeli, ngaleyo ndlela kulawula ukuqaliswa kokubhala.
Kuma-eukaryotes, ukulawulwa komsebenzi we-RNA polymerase kuyinkimbinkimbi kakhulu, okubandakanya amaprotheni atholakalayo ahlukahlukene kanye nokuguqulwa kwangemuva kokuhumusha. Isibonelo, i-phosphorylation ye-RNA polymerase nge-cyclin-dependent kinase ingashukumisa noma ivimbele ukulotshwa kofuzo oluthile. Ngaphezu kwalokho, izinto ezilotshiweyo njengezicishamlilo nezicindezeli zingasebenzisana ne-RNA polymerase futhi zilawule umsebenzi wayo.
Kafushane, ukulawulwa komsebenzi we-RNA polymerase kuyinqubo ebalulekile yokuvezwa kofuzo okufanele ngaphakathi kweseli. Ukuqonda lezi zindlela zokulawula kubalulekile ekuthuthukisweni kwezindlela zokwelapha ezintsha kanye nokuthuthukiswa kwebhayoloji yamangqamuzana.
Umehluko ekukhiqizeni kwe-mRNA phakathi kwe-eukaryote nama-prokaryote: qonda umehluko oyinhloko.
Ukwenziwa kwe-Messenger RNA (mRNA) kuyinqubo eyisisekelo ekuvezweni kwezakhi zofuzo, ehluka kakhulu phakathi kwama-eukaryotes nama-prokaryotes. Omunye umehluko omkhulu uhlobene ne -RNA polymerase , i-enzyme ebangela ukuhlanganiswa kwe-RNA kusuka ku-DNA.
Ku-prokaryotes, i-RNA polymerase yakhiwa i-subunit eyodwa, kuyilapho kuma-eukaryotes, yakhiwa ama-subunit amaningi. Le nkimbinkimbi yesakhiwo inika i-eukaryotic RNA polymerase ikhono lokubona futhi lilobe izifunda ezithile ze-DNA, njengabathuthukisi nezithuthukisi, ngokunembe kakhulu nangokulawula okukhulu.
Ngaphezu kwalokho, ukulawulwa kokubhala kuyinkimbinkimbi kakhulu kuma-eukaryote, okubandakanya ukusebenzisana kwezinto ezilotshiweyo, ukuguqulwa kwe-histone, nama-polymerase e-RNA akhethekile ukuze kulotshwe izinhlobo ezahlukene zofuzo. Ku-prokaryotes, ukuloba kuqondile futhi kulawulwa kancane, okuholela ekukhiqizweni kwe-mRNA ngokushesha nangempumelelo.
Lo mehluko ekukhiqizeni kwe-mRNA phakathi kwe-eukaryote nama-prokaryote kunemithelela ebalulekile ekulawuleni ukubonakaliswa kwezakhi zofuzo nokusebenza kwamangqamuzana ewonke. Ukuqonda umehluko wesakhiwo nokusebenza kwe-polymerase ye-RNA kubalulekile ukuze kucaciswe izindlela ezilawula ukuvezwa kofuzo ezinhlotsheni ezihlukene zezinto eziphilayo.
I-Polymerase: qonda ukubaluleka kwayo ku-DNA kanye nokuphindaphinda kwe-RNA.
I-Polymerase iyi-enzyme ebalulekile ku-DNA kanye nenqubo yokuphindaphinda kwe-RNA. Umsebenzi wayo ukuhlanganisa amaketanga amasha e-nucleotide asuka ku-DNA ekhona noma i-RNA molecule. I-Polymerase isebenza "njengomshini wokubhala wamangqamuzana," ikopisha ulwazi lofuzo futhi iqinisekise ukudluliswa kwayo okufanele kumaseli endodakazi.
Endabeni ye-RNA polymerase, le enzyme inesibopho sokuguqula i-DNA ibe ama-molecule e-RNA (mRNA) yesithunywa, kamuva ahunyushwa abe amaprotheni. I-RNA polymerase ibalulekile ekuvezeni izakhi zofuzo kanye nokuhlanganiswa kwamaprotheni abalulekile ekusebenzeni kwamangqamuzana.
Isakhiwo se-RNA polymerase siyahlukahluka phakathi kwama-prokaryote nama-eukaryote. Ku-prokaryotes, i-RNA polymerase yakhiwe ngamayunithi ambalwa, kuhlanganise ne-sigma subunit, ebona umgqugquzeli wofuzo futhi iqale ukuloba. Ku-eukaryotes, i-RNA polymerase iyinkimbinkimbi kakhulu, ehlanganisa amayunithi amancane amaningi anesibopho sokulawula ukulotshwa kwezinhlobo ezahlukene ze-RNA.
I-RNA polymerase idlala indima ebalulekile ekulawuleni ukubonakaliswa kofuzo, ekulawuleni ukuthi yiziphi izakhi zofuzo ezibhalwayo nokuthi nini. Ingathonywa izici eziningana, njengezimpawu zamaselula, amaprotheni okulawula, nokuguqulwa kwe-epigenetic.
Kafushane, i-RNA polymerase iyi-enzyme eyisisekelo yokuphindaphinda kwe-DNA ne-RNA, edlala indima ebalulekile ekuhlanganisweni kwama-molecule e-RNA esithunywa kanye nokulawulwa kokuvezwa kofuzo. Ukusebenza kwayo okunembile nokusebenza kahle kubalulekile ekugcineni ubuqotho be-genomic kanye nokusebenza okufanele kwamaselula.
Izinhlobo zama-polymerase e-RNA atholakala kuzinto eziphilayo ze-eukaryotic: ukuhlaziya okuningiliziwe.
Ama-polymerase e-RNA angama-enzyme abalulekile ekulotshweni kwe-DNA ku-RNA, inqubo eyisisekelo yokuvezwa kwezakhi zofuzo ezintweni eziphilayo. Ezintweni eziphilayo ze-eukaryotic, kunezinhlobo ezintathu eziyinhloko zama-polymerase e-RNA, ngayinye enesibopho sokulotshwa kwezinhlobo ezahlukene zofuzo.
I-RNA polymerase I inesibopho sokuloba izakhi zofuzo ezifaka ikhodi ye-ribosomal RNA (rRNA). Lolu hlobo lwe-RNA lubalulekile ekwakhiweni kwamaprotheni kumaseli e-eukaryotic. I-RNA polymerase II inesibopho sokuloba izakhi zofuzo ezifaka i-RNA (mRNA) yesigijimi, equkethe ulwazi lofuzo lokwenziwa kwamaprotheni. Okokugcina, i-RNA polymerase III inesibopho sokuloba izakhi zofuzo ezifaka ikhodi yokudlulisa i-RNA (tRNA) nezinye izinhlobo ze-RNA encane.
I-polymerase ye-RNA ngayinye yakhiwe ngamayunithi amaningana enza imisebenzi ethile phakathi nenqubo yokubhala. I-RNA polymerase II, ngokwesibonelo, yakhiwe amayunithi ayi-12 ahlukene asebenza ndawonye ukuze ahlanganise i-RNA yesigijimi ngokunemba nangempumelelo.
Ngaphezu kwalokho, ama-polymerase e-RNA ezinto eziphilayo ze-eukaryotic alawulwa izici eziningana zokuloba ezilawula ukuvezwa kwezakhi zofuzo ekuphenduleni izisusa zangaphakathi nezangaphandle. Lezi zici zokuloba ziqinisekisa ukuthi izakhi zofuzo zibhalwa ngesikhathi esifanele nangamanani alungile, okuqinisekisa i-homeostasis yeselula.
Kafushane, ama-polymerase e-RNA adlala indima ebalulekile ekulotshweni kwe-DNA ibe yi-RNA ezintweni eziphilayo ze-eukaryotic, iqinisekisa ukuvezwa okulungile kwezakhi zofuzo kanye nokuhlanganiswa kwamaprotheni abalulekile ekusindeni kweseli.
I-RNA polymerase: isakhiwo, imisebenzi, ama-prokaryotes, ama-eukaryotes
I-RNA polymerase iyinhlanganisela ye-enzyme ephethe ukuvumelanisa i-polymerization ye-molecule ye-RNA kusuka kuchungechunge lwe-DNA olusebenzisa njengethempulethi. Le nqubo iyisinyathelo sokuqala ekuvezweni kwezakhi zofuzo futhi ibizwa ngokuthi i-transcription. I-RNA polymerase ibopha i-DNA endaweni ethile eyaziwa ngokuthi i-promoter.
Le enzyme-kanye nenqubo yokubhala ngokujwayelekile-iyinkimbinkimbi kakhulu kuma-eukaryotes kunama-prokaryotes. Ama-eukaryote anama-polymerase e-RNA amaningi akhethekile ezinhlotsheni zofuzo ezithile, ngokungafani nama-prokaryote, lapho zonke izinhlobo zofuzo zibhalwa ngesigaba esisodwa se-polymerase.
Umthombo: Mina, Splette [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]
Ukwanda kwenkimbinkimbi phakathi kohlu lwe-eukaryotic ezintweni ezihlobene nokulotshwa kungenzeka kuhlobene nesistimu yokulawula izakhi zofuzo ejwayeleke kakhulu yezinto eziphilayo zamangqamuzana amaningi.
E-archaea, ukuloba kufana nenqubo eyenzeka kuma-eukaryotes, nakuba ane-polymerase eyodwa kuphela.
Ama-polymerase awenzi wodwa. Ukuze inqubo yokubhala iqale ngendlela efanele, ukuba khona kwezakhi zamaprotheni ezibizwa ngokuthi izici zokuloba kuyadingeka.
Isakhiwo
Ama-polymerase e-RNA anezimpawu ezinhle kakhulu ama-polymerase ebhaktheriya. Aqukethe amaketanga amaningi e-polypeptide. I-enzyme inama-subunits amaningana, abhalwe njenge-α, β, β′, kanye no-σ. I-subunit yokugcina iboniswe ukuthi ayihlanganyeli ngokuqondile ku-catalysis kodwa ihileleke ekubopheni i-DNA ethile.
Eqinisweni, uma siqeda i-subunit engu-σ, i-polymerase isengakwazi ukugqugquzela ukusabela kwayo okuhlobene, kodwa ezifundeni ezingalungile.
I-α subunit inesisindo samaDaltons angu-40.000 futhi kukhona amabili awo. Kuma-subunits u-β kanye no-β′, kukhona eyodwa kuphela, futhi anesisindo samaDaltons ayi-1 kanye ne-155.000, ngokulandelana.
Lezi zakhiwo ezintathu zitholakala kumongo we-enzyme, kuyilapho i-subunit ye-σ itholakala kude futhi ibizwa ngokuthi i-sigma factor. I-enzyme ephelele—noma i-holoenzyme—inesisindo esiphelele esingama-Daltons angu-480.000.
Ukwakheka kwe-RNA polymerase kuyahlukahluka kakhulu futhi kuncike eqenjini elifundwayo. Nokho, kuzo zonke izinto eziphilayo, iyi-enzyme eyinkimbinkimbi eyakhiwe amayunithi amaningana.
Imisebenzi
Umsebenzi we-RNA polymerase ukwenza polymerize ama-nucleotide ochungechunge lwe-RNA, olwakhiwe ngesifanekiso se-DNA.
Lonke ulwazi oludingekayo ekwakhiweni nasekuthuthukisweni kwento ephilayo lubhalwe ku-DNA yayo. Nokho, lolu lwazi aluhunyushwanga ngokuqondile kumaprotheni. Kudingeka isinyathelo esimaphakathi ukuze kudluliselwe ulwazi ku-molecule ye-RNA yesithunywa.
Lokhu kuguqulwa kolimi lwe-DNA lube yi-RNA kulamulwa yi-RNA polymerase, futhi lo mkhuba ubizwa ngokuthi ukuloba. Le nqubo ifana nokuphindaphinda kwe-DNA.
Ku-prokaryotes
Ama-prokaryote ayizinto eziphilayo ezineseli elilodwa ezingenayo i-nucleus echaziwe. Kuwo wonke ama-prokaryote, into ecwaningwe kakhulu yi- Escherichia coli . Leli gciwane lihlala njalo kuma-microbiota ethu futhi libe yisibonelo esihle kakhulu sezazi zezakhi zofuzo.
I-RNA polymerase yaqala ukuhlukaniswa kulesi sidalwa, futhi izifundo eziningi zokubhalwa kwemibhalo zenziwe ku- E. coli. Engqamuzaneni elilodwa laleli gciwane, singathola ama-molecule e-polymerase afinyelela ku-7000.
Ngokungafani nama-eukaryote anezinhlobo ezintathu zama-polymerase e-RNA, kuma-prokaryotes zonke izakhi zofuzo zicutshungulwa uhlobo olulodwa lwe-polymerase.
Ku-eukaryotes
Yini isakhi sofuzo?
I-Eukaryote yizinto eziphilayo ezine-nucleus eboshwe ulwelwesi kanye nama-organelle ahlukahlukene. Amangqamuzana e-Eukaryotic abonakala ngezinhlobo ezintathu zama-nuclear RNA polymerases, ngalinye linomthwalo wemfanelo wokulotshwa kwezakhi zofuzo ezithile.
"Ufuzo" akulona igama elilula ukulichaza. Ngokuvamile, sijwayele ukubiza noma yikuphi ukulandelana kwe-DNA okugcina kuhumushela kuphrotheni "ngofuzo." Nakuba isitatimende esingenhla siyiqiniso, kukhona futhi izakhi zofuzo umkhiqizo wazo wokugcina uyi-RNA (hhayi iphrotheni), noma izakhi zofuzo ezihilelekile ekulawuleni inkulumo.
Kunezinhlobo ezintathu zama-polymerase, okuthiwa I, II, kanye no-III. Ngezansi, sizochaza imisebenzi yabo:
I-RNA polymerase II
Izakhi zofuzo ze-protein-coding—ezibandakanya i-RNA yesithunywa—zilotshwa yi-RNA polymerase II. Ngenxa yokubaluleka kwayo ekuhlanganiseni amaprotheni, kube yi-polymerase ecwaningwe kakhulu ngabacwaningi.
Izici zokuloba
Lawa ma-enzyme awakwazi ukuqondisa inqubo yokubhala ngokwawo; zidinga ukuba khona kwamaprotheni abizwa ngokuthi izici zokuloba. Izinhlobo ezimbili zezinto zokulotshwa zingahlukaniswa: ezivamile nezingeziwe.
Iqembu lokuqala lihlanganisa amaprotheni ahilelekile ekubhalweni kwawo wonke ama-promoter e-polymerase II. Lawa akha indlela eyisisekelo yokubhalwa.
Kuzinhlelo ze -in vitro , izici ezinhlanu ezijwayelekile ezibalulekile ekuqalisweni kokubhalwa kwe-RNA polymerase II ziye zachazwa. Laba bagqugquzeli babelana ngokulandelana kokuvumelana okubizwa ngokuthi "ibhokisi le-TATA".
Isinyathelo sokuqala ekubhalweni kwe-transcription sihilela ukubopha isici esibizwa nge-TFIID ebhokisini le-TATA. Le phrotheni iyinkimbinkimbi enama-subunit amaningana - phakathi kwawo, indawo ethile yokubopha ebhokisini. Yakhiwe futhi ngama-peptide ayishumi nambili abizwa ngama-TAF ( izinto ezihlobene ne-TBP ).
Isici sesithathu esihilelekile yi-TFIIF. Ngemuva kokuqashwa kwe-polymerase II, izici ze-TFIIE kanye ne-TFIIH ziyadingeka ukuze kuqaliswe ukulotshwa.
I-RNA polymerase I no-III
I-Ribosomal RNAs izakhi ze-ribosomes. Ngaphezu kwe-ribosomal RNA, ama-ribosomes enziwe ngamaprotheni futhi anesibopho sokuhumusha i-molecule ye-RNA yesithunywa ibe amaprotheni.
Ama-RNA okudlulisa nawo abamba iqhaza kule nqubo yokuhumusha, okuholela ku-amino acid ezofakwa ochungechungeni lwe-polypeptide ekwakhiwa.
Lawa ma-RNA (i-ribosomal nokudluliswa) alotshwe ngama-RNA polymerases I no-III. I-RNA polymerase I iqondene ngqo nokulotshwa kwama-ribosomal RNAs amakhulu, aziwa ngokuthi 28S, 28S, kanye no-5.8S. U-S ubhekisela ku-coefficient ye-sedimentation, okungukuthi, amazinga e-sedimentation phakathi nenqubo ye-centrifugation.
I-RNA polymerase III inesibopho sokulotshwa kofuzo olufaka ama-RNA ama-ribosomal amancane (5S).
Ngaphezu kwalokho, inani lama-RNA amancane (khumbula ukuthi kunezinhlobo eziningana ze-RNA, hhayi nje isithunywa esaziwa kangcono, i-ribosomal, nama-RNA okudlulisa), njengama-RNA amancane enyukliya, alotshwe yi-RNA polymerase III.
Izici zokuloba
I-RNA polymerase I, ibekelwe ngokukhethekile ukulotshwa kofuzo lwe-ribosomal, idinga izici ezimbalwa zokulotshwa komsebenzi wayo. Izakhi zofuzo ezifaka ikhodi ye-ribosomal RNA zinokuphromotha otholakala cishe ngamapheya ayisisekelo angu-150 phezulu nomfula wesayithi lokuqala lokuloba.
Umthuthukisi ubonwa izici ezimbili zokulotshwa: i-UBF ne-SL1. Lokhu kubophezela ngokuhlanganyela kumgqugquzeli futhi kubuthe i-polymerase I, kwakha inkimbi yokuqalisa.
Lezi zici zakhiwe ngama-protein subunits amaningana. Ngokufanayo, i-TBP ibonakala iyisici esilotshiweyo esabiwe kuwo wonke ama-polymerase amathathu aku-eukaryote.
Ku-RNA polymerase III, izici zokuloba ezithi TFIIIA, TFIIIB, kanye ne-TFIIIC zikhonjiwe. Lokhu kubophezela ngokulandelana kokubhaliwe okuyinkimbinkimbi.
I-RNA polymerase kuma-organelles
Esinye sezici ezihlukanisayo zama-eukaryote ama-subcellular compartments abizwa ngokuthi ama-organelles. I-Mitochondria nama-chloroplasts ayisikhumbuzo se-enzyme eshiwo ngenhla, i-RNA polymerase, kubhaktheriya. Lawa ma-polymerase ayasebenza futhi abhala i-DNA etholakala kulawa ma-organelles.
Ngokusho kwe-endosymbiotic theory, ama-eukaryote avela esenzakalweni se-symbiotic lapho ibhaktheriya limboza elincane. Leli qiniso elibalulekile lokuziphendukela kwemvelo lichaza ukufana phakathi kwama-polymerase e-mitochondrial nama-polymerase ebhaktheriya.
Ku-archaea
Njengakubhaktheriya, e-archaea kukhona uhlobo olulodwa kuphela lwe-polymerase olunomthwalo wemfanelo wokubhala zonke izakhi zofuzo ze-unicellular organism.
Kodwa-ke, i-archaeal RNA polymerase ifana kakhulu ngesakhiwo ne-eukaryotic RNA polymerase. Afaka ibhokisi le-TATA nezinto ezilotshiweyo, ikakhulukazi i-TBP ne-TFIIB.
Ngokuvamile, inqubo yokubhala ku-eukaryotes ifana ncamashi naleyo etholakala ku-archaea.
Umehluko nge-DNA polymerase
Ukuphindaphinda kwe-DNA kuhlelwa yi-enzyme eyinkimbinkimbi ebizwa ngokuthi i-DNA polymerase. Nakuba le enzyme ivame ukuqhathaniswa ne-RNA polymerase—kokubili ikhuthaza ukwenziwa kwe-polymerization yeketango le-nucleotide ekuqondeni kuka-5' kuya ku-3'—iyahluka ngezindlela eziningana.
I-DNA polymerase idinga ingxenye encane ye-nucleotide ukuze iqalise ukuphindaphindwa kwe-molecule, ebizwa ngokuthi i-primer. I-RNA polymerase ingaqala ukwenziwa kwe-novo futhi ayidingi eyokuqala ukuze isebenze.
I-DNA polymerase iyakwazi ukubophezela kumasayithi amaningi eduze kwechromosome, kanti i-polymerase ibophezela kuphela kubathuthukisi bofuzo.
Ngokuphathelene nezindlela zokufunda ama-enzyme , lezo ze-DNA polymerase zaziwa kangcono, njengoba zingalungisa ama-nucleotide anephutha ahlulwe ngephutha.
Izinkomba
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