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