Ribosome Structure and Translation in Bacteria vs Eukaryotes

Ribosome size in bacteria

70S (30S + 50S subunits).

Ribosome size in eukaryotes

80S (40S + 60S subunits).

Bacterial 30S subunit composition

21 proteins and 1 rRNA.

Eukaryotic 40S subunit composition

33 proteins and 1 rRNA.

Bacterial 50S subunit composition

34 proteins and 2 rRNAs.

Eukaryotic 60S subunit composition

49 proteins and 3 rRNAs.

Initiator tRNA in bacteria

tRNA^fMet (formylmethionine).

Initiator tRNA in eukaryotes

tRNA^Met (methionine).

Initiation factors in bacteria

IF1, IF2, and IF3.

Initiation factors in eukaryotes vs bacteria

Eukaryotes require more initiation factors than bacteria.

mRNA binding to bacterial ribosome

Via the Shine-Dalgarno sequence.

mRNA binding to eukaryotic ribosome

Via recognition of the 7-methylguanosine cap at the 5′ end.

Start codon selection in bacteria

AUG, GUG, or UUG located just downstream of the Shine-Dalgarno sequence.

Start codon selection in eukaryotes

According to Kozak's rules.

Typical elongation rate in bacteria

15-20 amino acids per second.

Typical elongation rate in eukaryotes

2-6 amino acids per second.

Release factors for termination in bacteria

RF1, RF2, and RF3.

Release factors for termination in eukaryotes

eRF1 and eRF3.

Translation location in bacteria

Cytoplasm.

Translation location in eukaryotes

Cytosol.

Translation coupling to transcription in bacteria

Yes.

Translation coupling to transcription in eukaryotes

No.