initiation.txt

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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
Initiation in prokaryotes
- 1. N-formyl-methionine
- 2. HAS Shine-Dalgarno sequence (Shows ribosomes where to start)
- 3. Has Initiation factors 1, 2 & 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
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
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
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
eIF4E
- Binding of the 5' cap
- Important in the complex as it binds to the mRNA prior to scanning for AUG by 43S ribosome
eIF5
- Aidings in joining of 60S ribosomal subunit to 40S
- These eiF5 and eiF1 dissociate once 60S binds

Author

rincrocci

143986

Card Set

initiation.txt

Description

initiation factors

Updated

2012-03-26T19:57:40Z

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