Kauj Ruam thib ob hauv kev siv cov ntaub ntawv caj ces yog kev sib txuas ntawm cov protein molecule raws li tus xa xov RNA (kev txhais lus). Txawm li cas los xij, tsis zoo li kev sau ntawv, cov kab ke nucleotide tsis tuaj yeem muab txhais ua cov amino acid ncaj qha, vim tias cov tebchaw no muaj cov tshuaj sib txawv. Yog li, kev txhais lus yuav tsum muaj tus neeg nruab nrab hauv daim ntawv hloov RNA (tRNA), uas nws txoj haujlwm yog los txhais cov caj ces rau hauv "lus" ntawm cov amino acids.
Cov yam ntxwv ntawm kev hloov pauv RNA
Thauj RNAs lossis tRNAs yog cov khoom me me uas xa cov amino acids mus rau qhov chaw ntawm cov protein synthesis (rau hauv ribosomes). Tus nqi ntawm hom ribonucleic acid hauv lub cell yog kwv yees li 10% ntawm tag nrho RNA pas dej.
Zoo li lwm hom ribonucleic acids, tRNA muaj cov saw ntawm ribonucleoside triphosphates. Ntevcov nucleotide ib ntus muaj 70-90 units, thiab kwv yees li 10% ntawm cov molecule muaj pes tsawg leeg poob rau cov khoom me.
Vim qhov tseeb tias txhua tus amino acid muaj nws tus kheej cov cab kuj nyob rau hauv daim ntawv ntawm tRNA, lub cell synthesizes ntau ntau yam ntawm no molecule. Nyob ntawm seb hom kab mob muaj sia nyob, qhov ntsuas no txawv ntawm 80 txog 100.
Functions of tRNA
Hloov RNA yog tus xa khoom ntawm substrate rau protein synthesis uas tshwm sim hauv ribosomes. Vim lub peev xwm tshwj xeeb los khi ob qho tib si rau cov amino acids thiab rau cov qauv sib lawv liag, tRNA ua raws li kev hloov pauv hauv kev hloov cov ntaub ntawv caj ces los ntawm daim ntawv RNA mus rau cov protein. Kev sib cuam tshuam ntawm ib tus neeg nruab nrab nrog cov coding matrix, xws li hauv kev sau, yog raws li lub hauv paus ntsiab lus ntawm complementarity ntawm nitrogenous bases.
Lub luag haujlwm tseem ceeb ntawm tRNA yog lees txais cov amino acid units thiab thauj lawv mus rau lub cuab yeej ntawm cov protein synthesis. Tom qab cov txheej txheem kev ua haujlwm no yog lub ntsiab lus lom neeg loj heev - kev ua raws li txoj cai caj ces. Kev siv cov txheej txheem no yog ua raws li cov hauv qab no:
- tag nrho cov amino acids yog encoded los ntawm triplets ntawm nucleotides;
- rau txhua triplet (los yog codon) muaj ib qho anticodon uas yog ib feem ntawm tRNA;
- txhua tRNA tuaj yeem khi rau ib qho tshwj xeeb amino acid.
Yog li, cov amino acid ib ntus ntawm cov protein yog txiav txim siab los ntawm qhov twg tRNAs thiab nyob rau hauv qhov kev txiav txim yuav ntxiv cuam tshuam nrog tus xa xov RNA hauv cov txheej txheem.tshaj tawm. Qhov no tuaj yeem ua tau vim muaj cov chaw ua haujlwm hauv kev hloov pauv RNA, ib qho yog lub luag haujlwm rau kev xaiv txuas ntawm cov amino acid, thiab lwm yam rau kev khi rau codon. Yog li ntawd, cov haujlwm thiab cov qauv ntawm tRNA yog sib cuam tshuam.
Structure of transfer RNA
TRNA yog qhov tshwj xeeb hauv nws cov qauv molecular tsis yog kab. Nws suav nrog helical ob-stranded seem, uas yog hu ua stems, thiab 3 ib leeg-stranded loops. Nyob rau hauv cov duab, no conformation zoo li ib tug clover nplooj.
Cov kab hauv qab no yog qhov txawv ntawm tRNA qauv:
- txais;
- anticodon;
- Ydihydrouridyl;
- pseudouridyl;
- ntxiv.
Ob chav helix stems muaj 5 txog 7 Watson-Crickson khub. Thaum kawg ntawm tus txais qia yog ib txoj hlua me me ntawm cov nucleotides tsis sib xws, 3-hydroxyl uas yog qhov chaw ntawm kev txuas ntawm cov khoom sib txuam amino acid molecule.
Cov qauv cheeb tsam rau kev sib txuas nrog mRNA yog ib qho ntawm tRNA loops. Nws muaj cov tshuaj anticodon ntxiv rau qhov kev nkag siab triplet hauv tub txib RNA. Nws yog cov anticodon thiab qhov kawg txais uas muab lub adapter muaj nuj nqi ntawm tRNA.
Tertiary qauv ntawm ib molecule
"Cloverleaf" yog ib qho qauv thib ob ntawm tRNA, txawm li cas los xij, vim yog folding, lub molecule tau txais L-shaped conformation, uas yog tuav ua ke los ntawm hydrogen bonds ntxiv.
L-daim ntawv yog tus qauv tertiary ntawm tRNA thiab muaj ob txoj hauv kevperpendicular A-RNA helices muaj qhov ntev ntawm 7 nm thiab tuab ntawm 2 nm. Daim ntawv no ntawm cov molecule tsuas muaj 2 qhov kawg, ib qho muaj anticodon, thiab lwm yam muaj qhov chaw txais.
Ntawm ntawm tRNA khi rau amino acid
Ua kom cov amino acids (lawv txuas rau kev hloov RNA) yog ua los ntawm aminoacyl-tRNA synthetase. Cov enzyme no ib txhij ua 2 lub luag haujlwm tseem ceeb:
- catalyses tsim cov kev sib cog lus ntawm 3'-hydroxyl pawg ntawm cov qia txais thiab cov amino acid;
- muab lub hauv paus ntsiab lus ntawm kev xaiv kev sib tw.
Txhua ntawm 20 amino acids muaj nws tus kheej aminoacyl-tRNA synthetase. Nws tsuas tuaj yeem cuam tshuam nrog hom kev thauj khoom tsim nyog. Qhov no txhais tau hais tias cov anticodon ntawm tom kawg yuav tsum tau ntxiv rau triplet encoding no tshwj xeeb amino acid. Piv txwv li, leucine synthetase tsuas yog khi rau tRNA npaj rau leucine.
Muaj peb lub hnab ris nucleotide-binding nyob rau hauv aminoacyl-tRNA synthetase molecule, lub conformation thiab tus nqi ntawm uas yog complementary rau cov nucleotides ntawm tus coj anticodon nyob rau hauv tRNA. Yog li, enzyme txiav txim siab qhov xav tau kev thauj khoom molecule. Ntau zaus tsawg dua, cov kab ke nucleotide ntawm tus neeg txais qia ua haujlwm raws li kev lees paub.
