H3 Translation in eukaryotes

Eukaryotic ribosomes are larger (80S) and more complex than prokaryotic ribosomes (70S). Initiation is basically similar in prokaryotes and eukaryotes except that in eukaryotes at least nine initiation factors are involved (cf. three factors in prokaryotes), the initiating amino acid is methionine (cf. N-formylmethionine in prokaryotes), eukaryotic mRNAs do not contain Shine-Dalgarno sequences (so the AUG initiation codon is detected by the ribosome scanning instead), and eukaryotic mRNA is monocistronic (cf. some polycistronic mRNAs in prokaryotes). Initiation in eukaryotes involves the formation of a 48S preinitiation complex between the 40S ribosomal subunit, mRNA, initiation factors and Met-tRNA 61. The ribosome then scans the mRNA to locate the AUG initiation codon. The 60S ribosomal subunit now binds to form the 80S initation complex. 

Elongation in eukaryotes requires three eukaryotic initiation factors that have similar functions to the corresponding prokaryotic proteins. 

A single eukaryotic release factor recognizes all three termination codons and requires ATP for activity. 

Initiation The overall mechanism of protein synthesis in eukaryotes is basically the same 

Instant Notes in Biochemistry 2nd Edition, B.D. Hames N.M. Hooper, (c) 2000 BIOS Scientific Publishers Ltd, Oxford. 

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