The main difference between protein synthesis in prokaryotes and eukaryotes is that prokaryotes contain polycistronic mRNA, whereas eukaryotes contain monocistronic RNA.
Protein synthesis in prokaryotes and eukaryotes is the process of synthesizing new or regeneration of existing functional peptides. Although both processes have differences, prokaryote and eukaryote protein synthesis are similar processes.
Key Areas Covered
1. What is Protein Synthesis in Prokaryotes
– Definition, Structure, Function
2. What is Protein Synthesis in Eukaryotes
– Definition, Structure, Function
3. Similarities Between Protein Synthesis in Prokaryotes and Eukaryotes
– Outline of Common Features
4. Difference Between Protein Synthesis in Prokaryotes and Eukaryotes
– Comparison of Key Differences
Key Terms
Protein Synthesis in Eukaryotes, Protein Synthesis in Prokaryotes
What is Protein Synthesis in Prokaryotes
Protein synthesis in prokaryotes is the process of synthesizing new copies of existing, functional proteins in prokaryotes. It uses coded information in DNA in order to assemble amino acids in proteins. Meanwhile, transcription and translation are the two steps of prokaryotic protein synthesis. In prokaryotic transcription, the information on DNA is transcribed into mRNA. The transcription occurs inside the cytoplasm in prokaryotes. This produces a linear, single-stranded molecule of mRNA. On the other hand, prokaryotes contain many genes organized together, forming operons. However, the function of the proteins encoded by these genes is similar. Therefore, the genes in operons undergo transcription together.
Figure 1: RNA Transcription
Furthermore, the mRNA produced in prokaryotic transcription is polycistronic due to the presence of operons. This conserves the energy used in prokaryotic protein synthesis. On the other hand, an operon contains a single promoter. Here, environmental cues regulate this promoter. The operator region that is next to the promoter binds with regulator proteins that are either activator or repressor proteins. The producing mRNA is then subjected to translation, where the synthesis of peptide occurs.
What is Protein Synthesis in Eukaryotes
Protein synthesis in eukaryotes is the process of producing new copies of exciting functional proteins in eukaryotes. Same as in prokaryotes, the two steps of eukaryotic protein synthesis include transcription and translation. Transcription involves the synthesis of mRNA molecule that encodes the information about proteins coded in DNA. However, the genes in eukaryotes do not exist in operons. They are single genes. Therefore, the mRNA produced in the transcription of eukaryotic genes is monocistronic. On the other hand, the pre-mRNA of eukaryotic protein synthesis contains a 5’ cap.
Figure 2: Translation
Moreover, polyadenylation adds a poly-A tail at the 3’ end of eukaryotic pre-mRNA. Eukaryotic transcription occurs inside the nucleus, and the mRNA translocates into the cytoplasm for translation, which is the second step of protein synthesis in eukaryotes. In this process, mRNA is decoded into a sequence of amino acids of a peptide in ribosomes. In addition, eukaryotic ribosomes are 80S containing 40S and 60S subunits.
Similarities Between Protein Synthesis in Prokaryotes and Eukaryotes
- Protein synthesis of prokaryotes and eukaryotes synthesize new copies of the existing, functional proteins.
- The two steps of these processes are transcription and translation.
- The information of proteins coded in DNA is transcribed into an mRNA molecule to translate into an amino acid sequence of a functional protein by ribosomes.
- Both processes are highly regulated.
Difference Between Protein Synthesis in Prokaryotes and Eukaryotes
Definition
Protein synthesis in prokaryotes refers to the process of producing proteins by taking coded information from the cell DNA and using it to assemble amino acids into proteins in prokaryotes while protein synthesis in eukaryotes refers to the process by which protein forms by the transcription of DNA into mRNA and the translation of mRNA into proteins in eukaryotes.
mRNA
Prokaryotes contain polycistronic mRNA, while eukaryotes contain monocistronic mRNA.
Transcription and Translation
Prokaryotes have coupled transcription and translation, while eukaryotes have no coupled transcription and translation.
Polyribosomes
Moreover, prokaryotes contain linear polyribosomes, while eukaryotes contain circular polyribosomes.
5’ Cap in mRNA
Prokaryotes do not contain a 5’ cap on mRNA, while eukaryotes contain a 5’ cap on mRNA.
Ribosome Binding Site
In prokaryotes, AUG and start codon are next to the ribosome binding site, while first AUG in mRNA is used as no ribosomal binding site is present in eukaryotes.
First Methyonine
The first methionine is formyl methionine in prokaryotes, while the first methionine is unmodified in eukaryotes.
Ribosomes
Prokaryotes contain 70S ribosomes with 30S and 50S subunits, while eukaryotes contain 80S ribosomes with 40S and 70S subunits.
Conclusion
In brief, prokaryotic and eukaryotic protein synthesis are two types of processes that synthesize new copies of existing, functional proteins. However, the main difference between prokaryotic and eukaryotic protein synthesis is the type of mRNA used in the protein synthesis process. Usually, prokaryotes use polycistronic mRNA, while eukaryotes use monocistronic mRNA. Moreover, prokaryotes contain linear polyribosomes, and the ribosomes of prokaryotes are 70S. In addition, prokaryotic mRNA does not contain a 5’ cap and ribosome binding site. In comparison, eukaryotes have circular polyribosomes, and their ribosomes are 80S. However, eukaryotes do not have a ribosome binding site.
References:
- Protein Synthesis in Prokaryotes. Study.com, Retrieved May 1, 2023
- Eukaryotic Protein Synthesis. Study.com, Retrieved May 1, 2023.
Image Courtesy:
- “MRNA” By Kelvinsong – Own work (CC BY 3.0) via Commons Wikimedia
- “Ribosome mRNA translation en” By LadyofHats – Own Work (Public Domain) via Commons Wikimedia
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