Difference Between Prokaryotic and Eukaryotic Translation


Prokaryotic and Eukaryotic Translation

Translation is the process of protein synthesis in the cells. It is the second step in genetic expression in which the ribosomes decodes the information present in mRNA to synthesize proteins according the sequence of codons present in them with different amino acids. Translation is a universal process occurs in both prokaryotes and eukaryotes. The fundamental process of translation is same in prokaryotes and eukaryotes. Members of both groups uses information present in mRNA, which is came from the DNA by transcription, to synthesize proteins with ribosome as the machinery. This post summarized the similarities and differences between prokaryotic and eukaryotic translation process in an EASY but in-depth way.

Similarities of prokaryotic and eukaryotic translation:

@. Both groups uses mRNA template

@. In both groups mRNA is synthesized from the genetic molecule, DNA

@. Ribosome is the protein synthesis machinery in both groups

@. All the 20 amino acids are same in both groups

@. All the 61 codons are similar in both groups

@. In both groups, protein synthesis occurs in the cytoplasm

@. In both groups, translation is completed in four processes, (1). Initiation, (2). Elongation, (3). Translocation and (4). Termination

@. The process of peptide bond formation is similar in both groups

@. In both groups, tRNA pick up and bring the correct amino acid

@. In both groups the peptidyl transferase activity which catalyze the formation of peptide bond formation is done by rRNA molecules of larger sub-unit of ribosome (Ribozyme)

@. All the three stop codons are similar in both groups


Difference between prokaryotic and eukaryotic translation


Prokaryotic Translation: 

1.  Process: Transcription and translation are continuous process and occurs simultaneously in the cytoplasm

2.  Starting: 5’ end of mRNA is immediately available for translation

3.  Ribosome: 70S type

4.  Ribosome sub-units: 50S larger sub-unit and 30S smaller sub-unit

5.  rRNA of larger ribosome sub-unit: Two rRNA molecules 5S and 23S rRNA

6.  rRNA of smaller ribosome sub-unit: One type, 16S rRNA

7.  Smaller ribosome sub-unit proteins: 21 proteins

8.  Larger ribosome sub-unit proteins: 36 proteins

9.  Ribosome mass: 2700 kd

10. Endoplasmic reticulum absent and hence protein synthesizing ribosome freely distributed in the cytoplasm

11. mRNA is usually polycystronic

12. mRNA can acts as the template for the synthesis of many polypeptides

13. Translation initiation: Single type which is cap independent initiation

14. Start site: May have many start sites and SD sequences (Shine-Dalgarno sequence) all along the mRNA

15. SD Sequence: SD sequence present 8 nucleotide upstream of start codon. SD sequence act as the ribosome binding site

16. Kozak sequence: Kozak sequence absent in mRMA

17. Initiation codon: Usually AUG, occasionally GUG or UUG

18. Smaller subunit of ribosome (30S) recognize the SD sequence in the mRNA during translation initiation

19. First tRNA: First tRNA is special type namely Met-tRNAf

20. First amino acid: First amino acid in the protein synthesis (methionine) will be formylated

21. Initiation factors: Only three initiation factors are required, they are IF1, IF2, IF3

22. Elongation factors: Two types of elongation factors, EF – Tu and EF – Ts

23. Speed of translation: ~ 20 amino acids/second

24. Termination: Facilitated by three release factors, RF1, RF2, RF3

25. Only the formyl group from the first amino acid (methionine) is removed from the polypeptide after protein synthesis

26. Life span of mRNA: Short, few seconds to few minutes

27. IF3 prevents the association of ribosomal subunits in the absence of initiation complex

28. Post translational modifications: Post translational modifications of proteins takes place in the cytoplasm

Eukaryotic Translation:

1.  Process: Transcription and translation are separate process, transcription occurs in the nucleus whereas translation occurs in the cytoplasm

2.  Starting: The primary transcript is processed after transcription and then it is transported to the cytoplasm, then only the cytoplasmic ribosomes can initiate translation

3.   Ribosome: 80S type

4.  Ribosome sub-units: composed of 60S larger subunit and 40S smaller subunit

5.  rRNA of larger ribosome sub-unit: Three rRNA molecules, 5S, 5.8S and 28S rRNA

6.  rRNA of smaller ribosome sub-units: 18S rRNA

7.  Smaller ribosome sub-unit proteins: ~ 33 proteins

8.  Larger ribosome sub-unit proteins: ~49 proteins

9.  Ribosome mass: 4200 kd

10. Endoplasmic reticulum present, protein synthesizing ribosome usually attached to the ER

11. mRNA is always monocystronic

12. mRNA can act as the template for a single polypeptide

13. Translation initiation: Two types of translation initiation mechanisms. (1) Cap depended and (2) Cap independent

14. Start site: Always have only one start site which is located towards the 5’ region of mRNA

15. SD sequence: SD sequence is absent in mRNA

16. Kozak sequence: Kozak sequence present in the mRNA which is located few nucleotide upstream of start site. Kozak sequence assists initiation process of translation

17. Initiation codon: Initiation codon is AUG. occasionally GUG or CUG.

18. Smaller subunit of ribosome (40S) recognize the 5’ cap of mRNA during initiation

19. First tRNA: First tRNA is Met-tRNA

20. First amino acid: No fomylation of methionine, the first amino acid, will occurs

21. Initiation factors: Seven types of initiation factors are required for translation, they are eIF1, eIF2, eIF3, eIF4, eIF5A, eIF5B, eIF6

22. Elongation factors: Elongation factors are eEF1 and eEF2

23. Speed of translation: ~1 amino acid/second

24. Termination: Termination is facilitated by only one release factor eRF1

25. Usually the un-formylated first methionine as such is removed from the polypeptide after protein synthesis

26. Life span of mRNA: Life span of mRNA long, few hours to a day or sometimes more

27. eIF3 prevents the association of ribosomal subunits in the absence of initiation complex

28. Post translational modifications: Post translational modifications usually takes place in the endoplasmic reticulum or Golgi bodies or in the cytoplasm


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