I-anticodon iwukulandelana kwamanucleotide amathathu atholakala ekudluliseni i-RNA (tRNA) ehambisana nekhodoni ethile kusithunywa i-RNA (mRNA). Umsebenzi wayo oyinhloko ukubona nokubophezela ku-codon ehambisanayo ngesikhathi sokuhumusha, ukusiza ukufakwa kwe-amino acid elungile ochungechungeni olusanda kwakhiwa lwe-polypeptide.
Ngokungafani ne-codon, etholakala ku-mRNA futhi inquma ukulandelana kwe-amino acid ephrotheni, i-anticodon ikhona ku-tRNA futhi isebenza njengomxhumanisi phakathi kwe-mRNA kanye ne-amino acid ehambisanayo. Ngakho-ke, i-anticodon idlala indima ebalulekile ekunembeni kokuhumusha izakhi zofuzo kanye nokuhlanganiswa kwamaprotheni. Lo mshini uqinisekisa ukuthi ama-amino acid ahlanganiswa ngendlela efanele, okuholela ekwakhekeni kwamaprotheni asebenzayo.
Ibaluleke kangakanani i-anticodon enqubweni yokuhumusha izakhi zofuzo?
I-anticodon wuchungechunge lwama-nucleotide amathathu atholakala ku- molecule ye-RNA yokudlulisa (tRNA) . Idlala indima ebalulekile enkambisweni yokuhumusha izakhi zofuzo , okuyiyona enesibopho sokwenziwa kwamaprotheni avela emiyalweni equkethwe ku -RNA ye-messenger (mRNA).
I-anticodon ibalulekile ukuqinisekisa ukuthi ama-amino acid afanele ayengezwa kuchungechunge lwe-polypeptide ngesikhathi sokuhumusha. I-anticodon ngayinye iyahambisana ne -codon ethile ku-mRNA, okuvumela i-molecule ye-tRNA ukuthi iqaphele futhi ibophe kuyo. Lokhu kuhambisana kuqinisekisa ukuthi i-amino acid efanele ifakwa kuphrotheni eyakhiwayo, kulandela ikhodi yezakhi zofuzo yomhlaba wonke.
Ngaphezu kwalokho, i-anticodon isebenza njengendlela enembile ngesikhathi sokuhumusha izakhi zofuzo. Noma yiliphi iphutha ekufanisweni kwe-anticodon ne-codon kungabangela iphrotheni enephutha noma engasebenzi kahle, okungaba nemiphumela emibi kakhulu emzimbeni.
Ngamafuphi, i-anticodon ibalulekile enkambisweni yokuhumusha izakhi zofuzo, ukuqinisekisa ukufakwa okufanele kwama-amino acid ekwakhiweni kwamaprotheni nokugcina ubuqotho bekhodi yezakhi zofuzo. Ukubaluleka kwayo akunakubukelwa phansi, njengoba ibalulekile ekubonakalisweni okufanele kwezakhi zofuzo kanye nokusebenza kahle kwamaseli nezinto eziphilayo zizonke.
Umehluko phakathi kwe-anticodon ne-codon: qonda ukuhluka kwenqubo yokuhumusha kofuzo.
Inqubo yokuhumusha izakhi zofuzo ibalulekile ukuze ulwazi oluqukethwe ku-DNA lubhalwe lube amaprotheni. Kule nqubo, i-anticodon ne-codon zidlala indima ebalulekile, kodwa zihlukile emisebenzini yazo kanye nezakhiwo.
I- codon wuchungechunge lwama-nucleotide amathathu ku-messenger RNA (mRNA) olunquma ukuthi iyiphi i-amino acid ezofakwa kuprotheni ngesikhathi sokwenziwa kwayo. I-codon ngayinye ihambisana ne-amino acid ethile, ngaleyo ndlela yakha ikhodi yezakhi zofuzo.
Ngakolunye uhlangothi, i- anticodon iyi-sequence ehambisana ne-codon, ekhona ku-RNA yokudlulisa (tRNA). I-anticodon inesibopho sokubona nokuhlanganisa ne-codon ehambisanayo ngesikhathi sokuhumusha, ukuqinisekisa ukuthi i-amino acid efanele ingeziwe ku-polypeptide chain eyakhiwayo.
Ngakho-ke, nakuba i-codon isebenza "njengekhodi" enquma ukulandelana kwe-amino acid kuphrotheni, i-anticodon isebenza "njengotolika" oqinisekisa ukuhunyushwa okulungile kwale khodi. Kokubili kubalulekile enqubweni yokwenziwa kwamaprotheni kanye nokugcina ubuqotho bezakhi zofuzo.
Qonda ukuthi iyini i-anticodon kanye nokubaluleka kwayo ekuhlanganiseni amaprotheni.
I-anticodon iwukulandelana kwezisekelo ezintathu ze-nitrogen ezikhona ekudluliselweni kwe-RNA (tRNA) ezihambisana nokulandelana kwezisekelo ezintathu okubizwa ngokuthi i-codon ku-messenger RNA (mRNA). Lokhu kuhambisana phakathi kwe-anticodon ne-codon kubalulekile ekuhlanganiseni amaprotheni kuma-ribosomes.
Umsebenzi oyinhloko we-anticodon ukuqinisekisa ukuthi i-amino acid efanele yengezwa ochungechungeni lwe-polypeptide ngesikhathi sokuhumusha kwe-mRNA. I-anticodon ngayinye ihlotshaniswa ne-amino acid ethile, futhi lapho i-codon ehambisanayo ibonwa, i-tRNA ihambisa i-amino acid efanelekile ukuze kuhlanganiswe amaprotheni.
Kubalulekile ukuqaphela ukuthi ama-anticodon aqondile ku-codon ngayinye, aqinisekisa ukunemba ekwakhekeni kwamaprotheni. Noma yiliphi iphutha noma ukuguqulwa kwalolu chungechunge kungaholela kuphrotheni engasebenzi noma ngisho nezifo zofuzo.
Kafushane, i-anticodon idlala indima ebalulekile ekuhunyushweni kwekhodi yofuzo, iqinisekisa ukulandelana okufanele kwe-amino acid ekuhlanganiseni kwamaprotheni. Ngakho-ke, ukuqonda kubalulekile ukuqonda ukusebenza kwezinqubo zamangqamuzana nokubonakaliswa kofuzo.
Qonda indima ye-codon ku-protein synthesis nokubaluleka kwayo kule nqubo.
I-codon iwukulandelana kwama-nucleotide amathathu kusithunywa i-RNA ehambisana ne-amino acid ethile ngesikhathi sokuhlanganiswa kwamaprotheni. Isebenza "njengekhodi" etshela umshini weselula ukuthi iyiphi i-amino acid okufanele yengezwe ochungechungeni lwamaprotheni akhiwayo. I-codon ngayinye ihambisana ne-anticodon ekudluliseni i-RNA, ephethe i-amino acid ehambisanayo.
I-codon ibalulekile enqubweni yokwenziwa kwamaprotheni, njengoba ngaphandle kwayo, ulwazi lofuzo oluqukethwe ku-DNA alukwazanga ukuguqulwa lube amaprotheni asebenzayo. Iqinisekisa ukunemba kokuhlanganiswa kweketanga le-amino acid, iqinisekisa ukuthi iphrotheni yokugcina inokulandelana okufanele ukwenza imisebenzi yayo emzimbeni.
Ngakolunye uhlangothi, i-anticodon iwukulandelana okuhambisana nekhodoni ekudluliseni i-RNA. Ibophezela ku-codon ngesikhathi sokuhumusha i-RNA yesithunywa, kusiza ukungezwa kwe-amino acid efanele ochungechungeni lwamaprotheni. Ama-anticodon abalulekile ekuqinisekiseni ukuhunyushwa okulungile kolwazi lofuzo lube amaprotheni.
Kafushane, ama-codon nama-anticodon adlala indima ebalulekile ekuhlanganiseni amaprotheni, aqinisekise ukunemba nokwethembeka kokuhunyushwa kwekhodi yofuzo kumaprotheni asebenzayo. Ukuqonda ukusebenzisana phakathi kwalokhu kulandelana kubalulekile ukuze uqonde ukuthi amaprotheni ahlanganiswa kanjani ngaphakathi kwamaseli.
I-Anticodon: Incazelo, Imisebenzi kanye Nomehluko nge-Codon
I- anticodon wuchungechunge lwama-nucleotide amathathu akhona ku-molecule ye-RNA yokudlulisa (tRNA), umsebenzi wayo ukuqaphela olunye uchungechunge lwama-nucleotide amathathu akhona ku-molecule ye-messenger RNA (mRNA).
Lokhu kuqashelwa phakathi kwama-codon nama-anticodon ku-antiparallel; okusho ukuthi, eyodwa itholakala ku-5 '-> 3' inkomba ngenkathi enye ihlanganiswe ku-3 '-> 5'. Lokhu kuqaphela phakathi kokulandelana kwama-nucleotide amathathu (ama-triplets) kubalulekile enqubweni yokuhumusha; okungukuthi, ekuhlanganisweni kwamaprotheni ku-ribosome.
Ngakho-ke, ngesikhathi sokuhumusha, ama-molecule e-RNA yesithunywa "afundwa" ngokuqashelwa kwama-codon awo ngama-anticodon of transfer RNAs. Lawa ma-molecule aqanjwe kanjalo ngoba adlulisela i-amino acid ethile ku-molecule yeprotheni eyakhiwa ku-ribosome.
Kunama-amino acid angama-20, ngalinye lifakwe ikhodi ngamathathu athile. Kodwa-ke, amanye ama-amino acid afakwe ikhodi ngamathathu angaphezu kweyodwa.
Ngaphezu kwalokho, amanye ama-codon aqashelwa ama-anticodon ekudluliseni ama-molecule e-RNA angenawo ama-amino acid anamathiselwe; lezi zibizwa ngokuthi ama-stop codon.
Incazelo yokwenza
I-anticodon yakhiwa ukulandelana kwama-nucleotide amathathu angaqukatha noma yiziphi izisekelo ze-nitrogenous ezilandelayo: i-adenine (A), i-guanine (G), i-uracil (U) noma i-cytosine (C) ngenhlanganisela yama-nucleotide amathathu, ukuze isebenze njengekhodi.
Ama-anticodon ahlala etholakala kuma-molecule e-RNA futhi ahlala esendaweni engu-3'->5'. Ukwakheka kwalawa ma-tRNA kufana neqabunga le-clover, ukuze lihlukaniswe libe izihibe ezine (noma ukuphenduka); kwesinye sezihibe kukhona i-anticodon.
Ama-Anticodon abalulekile ukuze kuqashelwe ama-codon e-RNA yesithunywa futhi, ngenxa yalokho, inqubo yokwakheka kwamaprotheni kuwo wonke amaseli aphilayo.
Imisebenzi
Umsebenzi oyinhloko wama-anticodon ukuqashelwa okuqondile kwama-triplets akha ama-codon kuma-molecule e-RNA esithunywa. Lawa ma-codon ayimiyalo ekopishwe ku-molecule ye-DNA ukuze inqume ukuhleleka kwama-amino acid ephrotheni.
Njengoba okulotshiweyo (ukuhlanganiswa kwamakhophi e-RNA esithunywa) kwenzeka ku-5'->3', amakhodoni e-RNA esithunywa analo mumo. Ngakho-ke, ama-anticodon akhona kuma-molecule e-RNA yokudlulisa kufanele abe nomumo ophambene, 3'->5'.
Le nyunyana ingenxa yokuhambisana. Isibonelo, uma i-codon ingu-5'-AGG-3′, i-anticodon ingu-3'-UCC-5′. Lolu hlobo lokusebenzelana okuqondile phakathi kwama-codon nama-anticodon kuyisinyathelo esibalulekile esivumela ukulandelana kwe-nucleotide ku-RNA yesithunywa ukuthi ihlanganise ukulandelana kwe-amino acid ngaphakathi kwephrotheni.
Umehluko phakathi kwe-anticodon ne-codon
Ama-Anticodon amayunithi e-trinucleotide kuma-tRNA, ahambisana nama-codon aku-mRNAs. Avumela ama-tRNA ukuthi anikeze ama-amino acid alungile ngesikhathi sokukhiqizwa kwamaprotheni. Ama-Codon, ngakolunye uhlangothi, amayunithi e-trinucleotide ku-DNA noma i-mRNA ekhodi ye-amino acid ethile ekuhlanganiseni kwamaprotheni.
Ama-Anticodon ayisixhumanisi phakathi kokulandelana kwe-nucleotide ye-mRNA kanye nokulandelana kwama-amino acid amaprotheni. Esikhundleni salokho, ama-codon adlulisela ulwazi lofuzo olusuka ku-nucleus, lapho i-DNA itholakala khona, kuya kuma-ribosomes lapho ukuhlanganiswa kwamaprotheni kwenzeka khona.
I-anticodon itholakala engalweni ye-Anticodon ye-molecule ye-tRNA, ngokungafani nama-codon, atholakala kuma-molecule e-DNA kanye ne-mRNA.
- I-anticodon ihambisana ne-codon yayo. Ngokuphambene, i-codon eku-mRNA ihambisana ne-nucleotide triplet yofuzo olunikeziwe ku-DNA.
– I-tRNA iqukethe i-anticodon eyodwa. Ngakolunye uhlangothi, i-mRNA iqukethe ama-codon amaningana.
I-equilibrium hypothesis
I-hypothesis yokulinganisa iphakamisa ukuthi ukuhlangana phakathi kwe-nucleotide yesithathu yesithunywa se-RNA codon kanye ne-nucleotide yokuqala yokudluliswa kwe-anticodon ye-RNA akucaci kahle kunokuhlangana phakathi kwamanye ama-nucleotide amabili e-triplet.
UCrick uchaze lesi simo ngokuthi "ukuzamazama" endaweni yesithathu yekhodoni ngayinye. Kukhona okwenzekayo kulesi sikhundla esivumela amalunga ukuthi aqine kancane kunokujwayelekile. Kwaziwa nangokuthi i-oscillation noma i-tamboleo.
Le hypothesis ye-Crick wobble ichaza ukuthi i-anticodon ye-tRNA enikeziwe ingahlangana kanjani nama-codon amabili noma amathathu ahlukene e-mRNA.
U-Crick uphakamise ukuthi ngenxa yokuthi ukumatanisa kwesisekelo (phakathi kwesisekelo esingu-59 se-anticodon ku-tRNA kanye nesisekelo esingu-39 se-codon ku-mRNA) kuqinile kunokuvamile, okunye "ukuzamazama" noma ukuncishiswa kobudlelwane kuvunyelwe kule sayithi.
Njengomphumela, i-tRNA eyodwa ngokuvamile ibona ama-codon amabili noma amathathu ahlobene acacisa i-amino acid enikeziwe.
Ngokuvamile, amabhondi e-hydrogen phakathi kwezisekelo zama-anticodon e-tRNA nama-codon e-mRNA alandela imithetho eqinile yokumatanisa okuyisisekelo kuphela ezisekelweni ezimbili zokuqala ze-codon. Kodwa-ke, lo mphumela awenzeki kuzo zonke izikhundla zesithathu zawo wonke amakhodoni we-mRNA.
I-RNA nama-amino acid
Ngokusekelwe ekucabangeni okuxegayo, kwabikezelwa ukuthi kuzoba khona okungenani ama-RNA amabili okudluliselwa kwe-amino acid ngayinye nama-codon abonisa ukuwohloka okuphelele, okubonakale kuyiqiniso.
Le mbono iphinde yabikezela ukuvela kwama-RNA amathathu okudlulisa ama-serine codon ayisithupha. Ngempela, ama-tRNA amathathu e-serine abonakalisiwe:
– I-tRNA ye-serine 1 (i-anticodon AGG) ibophezela kumakhodoni i-UCU ne-UCC.
– I-tRNA ye-serine 2 (i-anticodon ye-AGU) ibophezela kumakhodoni we-UCA kanye ne-UCG.
– I-tRNA ye-serine 3 (i-anticodon UCG) ibophezela kuma-codons AGU kanye ne-AGC.
Lokhu kucaciswa kwaqinisekiswa ngokubopha okuvuselelwe kwe-aminoacyl-tRNA trinucleotides ehlanzekile kuma-ribosomes in vitro.
Ekugcineni, ama-RNA amaningana okudlulisa aqukethe i-inosine eyisisekelo, eyenziwe nge-purine hypoxanthine. I-Inosine ikhiqizwa ukuguqulwa kwe-post-transcriptal ye-adenosine.
I-Crick's wobble hypothesis yabikezela ukuthi uma i-inosine ikhona ekupheleni kuka-5' kwe-anticodon (indawo enyakazayo), ihlotshaniswa ne-uracil, i-cytosine, noma i-adenine ku-codon.
Ngempela, i-alanyl-tRNA ehlanzekile equkethe i-inosine (I) endaweni engu-5' ye-anticodon ibophezela kuma-ribosomes acushiwe e-trinucleotide e-GCU, GCC, noma i-GCA.
Umphumela ofanayo utholwe ngenye i-tRNA ehlanziwe equkethe inosine endaweni engu-5' ye-anticodon. Ngakho-ke, i-wobble hypothesis ka-Crick ichaza kahle kakhulu ubudlelwano phakathi kwe-tRNA nama-codon, uma kubhekwa ikhodi yofuzo, eyonakele kodwa eyaliwe.
Izinkomba
- Brooker, R. (2012).I-Genetics Concepts (uhlelo loku-1). Inkampani yakwaMcGraw-Hill Companies, Inc.
- UBrown, T. (2006). IGenomes 3 ( I-3º ). Isayensi yeGarland
- Griffiths, A., Wessler, S., Carroll, S., kanye no-Doebley, J. (2015).Isingeniso Sokuhlaziywa Kwezofuzo (Isiqephu sesi-11). W.H. Freeman
- Lewis, R. (2015).Izakhi Zofuzo Zabantu: Imiqondo kanye Nezicelo (uhlelo loku-11). Imfundo yaseMcGraw-Hill.
- Snustad, D., & Simmons, M. (2011).Izimiso Zofuzo (6th ed.). UJohn Wiley kanye namadodana.