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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
ID
143986
Card Set
initiation.txt
Description
initiation factors
Updated
3/26/2012, 7:57:40 PM
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