Qhov sib txawv tseem ceeb ntawm kev pib txhais lus prokaryotic thiab eukaryotic yog qhov pib txhais lus prokaryotic tshwm sim ntawm 70S ribosomes thaum eukaryotic txhais lus pib tshwm sim ntawm 80S ribosomes.
Kev txhais lus lossis kev sib txuas ntawm cov protein yog cov txheej txheem lom neeg uas tshwm sim hauv cytoplasm. Nws pib los ntawm peb kauj ruam: pib, elongation thiab xaus. Cov txheej txheem no suav nrog kev txhais cov nucleotide triplets lossis codons tam sim no nyob rau hauv tus xa xov RNA (mRNA) ib ntus rau hauv cov amino acid ib ntus. Kev txhais lus yog ua los ntawm ribosomes thiab cov enzymes tshwj xeeb. Cov no catalyze tsim cov polypeptide raws li mRNA template.
Kev txhais lus Prokaryotic yog dab tsi?
Prokaryotic txhais lus pib yog kev khi ntawm 30S ribosomal subunit ntawm ribosome mus rau 5' kawg ntawm mRNA nrog kev pab los ntawm prokaryotic pib yam. Lub synthesis ntawm cov proteins pib nrog kev tsim ntawm qhov pib complex. Kev pib ua haujlwm muaj 30S ribosome, mRNA template, pib yam xws li IF-1, IF-2 thiab IF-3 thiab tshwj xeeb pib tRNA. Hauv prokaryotes, Shine Dalgarno ib ntus koom nrog hauv kev txheeb xyuas cov ribosome los pib txhais lus. Ci Dalgarno ib ntus khi nrog 30S ribosomal subunit ntawm mRNA template. Hauv cov kauj ruam no, IF-3 plays lub luag haujlwm tseem ceeb. Tus pib tRNA ces ua ke nrog pib codon AUG. Qhov no tRNA molecule thauj cov amino acid methionine.
Daim duab 01: Kev txhais lus Prokaryotic
Formylation ntawm methionine yog txheej txheem tseem ceeb uas tshwm sim hauv prokaryotes. Yog li, formylated methionine ua raws li thawj cov amino acid hauv kev txhais lus prokaryotic. Kev khi ntawm tRNA thiab methionine (fMet) yog kho los ntawm IF-2. Lub 30S ribosomal subunit ua ke nrog fMet, IF-1, IF-2 thiab IF -3 tsim qhov kev pib ua haujlwm. Lub hydrolysis ntawm GTP ntawm IF-2 thiab tso tawm tag nrho cov kev pib ua haujlwm tso cai rau kev khi ntawm 30S ribosomal subunit rau 50S ribosomal subunit los tsim ib qho kev ua haujlwm siab ribosome, tseem hu ua kev txhais lus complex. Txij li thaum GTP yog hydrolysed, kev khi ntawm cov subunits yog irreversibly spontaneous thiab yuav tsum tau lub zog los txiav txim txhais lus.
Kev txhais lus Eukaryotic yog dab tsi?
Eukaryotic txhais lus pib yog cov txheej txheem uas tus pib tRNA, 40S thiab 60S ribosomal subunits raug khi los ntawm eukaryotic pib yam (eIF) rau hauv 80S ribosome ntawm qhov pib codon ntawm mRNA. Eukaryotic txhais lus pib yam tseem ceeb, mRNA cov ntawv sau tseg, thiab cov ribosome feem ntau koom nrog cov txheej txheem pib. Cov txheej txheem pib khi rau 40s ribosomal subunit. Qhov pib qhov tseem ceeb eIF3 tiv thaiv kev khi ntxov ntxov ntawm ob lub subunits, thaum eIF4 ua raws li cap-binding protein. Kev txhais lus pib qhov tseem ceeb eIF2 xaiv tus nqi pib tRNA thiab khi nrog methionine los ua Met-tRNA. Cov molecule no tsis yog formylated. Tom qab cov txheej txheem khi no, ib qho ternary complex yog tsim, uas yog hu ua eIF2 / GTP / Met-tRNA. Qhov ternary complex no khi nrog lwm cov eIFs rau 40S subunit los tsim 43S preinitiation complex.
Daim duab 02: Eukaryotic Translation Initiation
Qhov kev ua ntej no nrog cov protein ntau txav raws mRNA saw ntawm 3 'kawg mus txog qhov pib codon. Cov txheej txheem no yog hu ua scanning ntawm mRNA. GTP hydrolysis yuav siv qhov chaw ntawm eIF2 uas ua rau lub dissociation ntawm txhais lus pib yam tseem ceeb los ntawm 40s subunit ua rau kev tsim ntawm tag nrho ribosome complex. Qhov no yog qhov kawg ntawm kev pib txhais lus eukaryotic thiab pib mus rau theem elongation.
Zoo sib xws ntawm Prokaryotic thiab Eukaryotic Translation Initiation
- Ob txheej txheem siv mRNA template.
- tRNA coj cov amino acid kom raug hauv ob txoj haujlwm.
- Ob lub ribosomal subunits koom nrog kev pib txhais lus.
- GTP hydrolysis tshwm sim hauv ob txoj hauv kev los qhib kev pib txhais lus.
- AUG ua raws li pib codon rau ob txheej txheem.
Qhov txawv ntawm Prokaryotic thiab Eukaryotic Translation Initiation
Prokaryotic txhais lus pib tshwm sim ntawm 70s ribosomes, thaum pib txhais lus eukaryotic tshwm sim ntawm 80s ribosomes. Yog li, qhov no yog qhov sib txawv tseem ceeb ntawm kev pib txhais lus prokaryotic thiab eukaryotic. Ntxiv mus, kev pib txhais lus prokaryotic yog txheej txheem cap-independent, thaum pib txhais lus eukaryotic yog cap-dependent thiab cap-independent. Yog li, qhov no yog lwm qhov sib txawv tseem ceeb ntawm kev pib txhais lus prokaryotic thiab eukaryotic. Tsis tas li ntawd, cov saw pib pib cov amino acids ntawm prokaryotic translation pib thiab eukaryotic translation pib yog N-formyl methionine thiab methionine, feem.
Cov infographic hauv qab no suav nrog qhov sib txawv ntawm kev pib txhais lus prokaryotic thiab eukaryotic hauv daim ntawv teev npe rau ib sab ntawm kev sib piv.
Summary – Prokaryotic vs Eukaryotic Translation Initiation
Kev txhais lus yog txheej txheem lom neeg uas tshwm sim hauv cytoplasm. Kev pib yog thawj kauj ruam ntawm kev txhais lus. Ib qho mRNA transcript ua tus qauv rau ob qho tib si prokaryotic thiab eukaryotic txhais lus pib. Prokaryotic txhais lus pib yog kev khi ntawm 30S ribosomal subunit ntawm ribosome mus rau 5' kawg ntawm mRNA nrog kev pab los ntawm prokaryotic pib yam. Cov kev pib muaj xws li IF-1, IF-2 thiab IF-3, thaum 70s ribosomes ua raws li lub ntsiab lus txhais tshuab koom nrog hauv cov txheej txheem pib. Eukaryotic txhais lus pib yog cov txheej txheem uas tus pib tRNA, 40S thiab 60S ribosomal subunits raug khi los ntawm eukaryotic pib yam tseem ceeb (eIF) rau hauv 80S ribosome ntawm qhov pib codon ntawm mRNA. Cov kev pib muaj xws li eIF-1, eIF2, eIF-3, eIF4, eIF5 thiab eIF6 thaum 80s ribosomes ua lub tshuab rau kev pib txhais lus hauv eukaryotes. Yog li, qhov no yog cov ntsiab lus ntawm qhov sib txawv ntawm kev pib txhais lus prokaryotic thiab eukaryotic.
