eukaryotic translation
DESCRIPTION
Eukaryotic Translation. mRNA tRNA rRNA. mRNA. -monocistronic -1,000-2,000 bases long -methylated at 5’cap -100-200 bases of poly A at 3’end -nontranslated 5’ reader < 100 bases -nontranslated 3’ tailer ~ 1,000 bases - AUG as the INITIATOR -UAA,UAG,&UGA as TERMINATOR. - PowerPoint PPT PresentationTRANSCRIPT
Eukaryotic Translation
mRNA tRNA rRNA
-monocistronic-1,000-2,000 bases long-methylated at 5’cap-100-200 bases of poly A at 3’end-nontranslated 5’ reader < 100 bases-nontranslated 3’ tailer ~ 1,000 bases- AUG as the INITIATOR-UAA,UAG,&UGA as TERMINATOR
mRNA
Fig5.16 Expression of mRNA
-removal of Poly(A) need for decapping enzyme
-Poly(A)-binding protein, PABP on Poly(A) prevents the decapping enzyme from binding to the 5’end
Life Cycle of Eukaryotic mRNA
AU-rich sequence, called ARE
~50 bases in 3’ tailer -AUUUA, more repeated-trigger destabilization
TRE sequence
- contain strm-loop structures for protein binding
-Protein inhibit destabilizing
tRNA
Met-tRNAi for initiation
Met-tRNAm for elongation
- No formylated Methionine-has an unusual tertiary structure, modofied by phosphorylation of the 2’ribose position
Eukaryotic Ribosome
The right context for Recognization
-AUG-the most important seq.GCCA
GCCAUGG, purine three bases before AUG and Gimmediately following it.
CAP; for a stable complex to be formed at initiation codon
Ternary complex;-Met-tRNAi
-eIF2-GTP
Eukaryotic Initiation
*form ternary complex*bind free 40S*attach the 5’ end
Initiation Factors
*bind 5’ cap*unwind mRNA*bind subunit initiation complex*support 60S joining
Elongation Factors:
EF-Tu, load aminoacyl tRNA
EF-Ts, GDP to GTP
Translocation:
Peptidyl transferase,synthesis peptide
EF-Tu
EF-G
Fig.6.27