initiation.txt

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Author:
rincrocci
ID:
143986
Filename:
initiation.txt
Updated:
2012-03-26 15:57:40
Tags:
initiation
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Description:
initiation factors
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  1. Initiation in eukaryotes
    • Initiation is the first step in translation
    • 1. begins with METHIONINE
    • 2. NO Shine-Dalgarno sequence
    • 3. mRNA HAS 5' CAP
    • 4. 12 Initiation factors
  2. Initiation in prokaryotes
    • 1. N-formyl-methionine
    • 2. HAS Shine-Dalgarno sequence (Shows ribosomes where to start)
    • 3. Has Initiation factors 1, 2 & 3
  3. eIF1 role
    • Bind directly to 40S ribosomal subunit to promote conformational change
    • Recognizes START CoDON
    • Binds near P-Site on 40S subunit: may mimic A-site bound tRNA to prevent aatRNA from bindng during initiation
  4. eIF1A role
    • Binds to 40S subunit to promote conformational changes
    • ENHANCES eIF1's ability to DISSOCIATE assembled complexes
    • Mediates 48S complex assembly (40S ribosome and ternary complex)
    • 48S complex assembly is EXCLUSIVELY at START codon
  5. eIF3 role
    • 1. Stabilizes TC binding of 40S
    • 2. Recruits mRNAs to 40s subunits
    • 3. Assists in scanning of 5' UTR of mRNA
    • 4. Aids in AUG START codon recognition
    • 5. PREVENTS spontaneous RE-Association of 40S and 60S subunits during initiation
    • consists of 13 subunits
    • 5 subunits serve as scaffolding
  6. eIF4F
    • Binds to 5' end of mRNA
    • Heterotrimer consisting of 6 factors
    • 1. stimulating eIF4A helicase
    • 2. helicase unwinding 5' structure
    • 3. scaffold protein (eiF4G)
    • 4. binding of 5' CAP (eiF4E)
    • 5. binding 3' poly A tail
    • 6. binding two other factors
  7. eIF4E
    • Binding of the 5' cap
    • Important in the complex as it binds to the mRNA prior to scanning for AUG by 43S ribosome
  8. eIF5
    • Aidings in joining of 60S ribosomal subunit to 40S
    • These eiF5 and eiF1 dissociate once 60S binds

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