Question

What are the major differences between translation in bacteria and translation in eukaryotes?

Short answer

Answer: The major differences between translation in bacteria and eukaryotes include differences in ribosome structure (70S in bacteria vs. 80S in eukaryotes), translation initiation (Shine-Dalgarno sequences in bacteria vs. 5' cap and Kozak sequence recognition in eukaryotes), differences in initiation and elongation factors, and termination processes (distinct release factors for bacteria vs. a single release factor for eukaryotes).

Step-by-step solution

Translation Process Overview

The translation process is essential for all forms of life. It involves converting the genetic information encoded in messenger RNA (mRNA) into a sequence of amino acids that form a protein. This process can be divided into three stages: initiation, elongation, and termination. Both bacteria and eukaryotes share these three stages, but there are several key differences in how they carry out the process.

Ribosome Structure Comparison

In both bacteria and eukaryotes, translation takes place on ribosomes. However, there are differences in ribosome structure between the two. Bacterial ribosomes are smaller, consisting of two subunits: 30S and 50S, which come together to form a complete 70S ribosome. In eukaryotes, ribosomes are larger, consisting of two subunits: 40S and 60S, forming an 80S ribosome. These differences in size and subunit composition affect the way translation occurs in each domain.

Initiation Process Comparison

During initiation, the ribosome assembles at the start codon on the mRNA strand. In bacteria, this occurs through Shine-Dalgarno sequences, which are specific base-pair sequences recognized by ribosomal RNA in the 30S subunit. In contrast, eukaryotic translation initiation involves the recognition of the 5' cap and Kozak sequence, a conserved sequence surrounding the start codon. Additionally, there are differences in the number and function of initiation factors (IFs) between bacteria and eukaryotes, which are proteins that aid in assembling the ribosome on the mRNA.

Elongation Process Comparison

During elongation, amino acids are added to the growing polypeptide chain. This process is highly conserved in both bacteria and eukaryotes, however, there are again differences in the elongation factors (EFs) involved. Bacterial translation requires three types of elongation factors: EF-Tu, EF-Ts, and EF-G, whereas the eukaryotic equivalent involves eEF1A (similar to EF-Tu), eEF1B (similar to EF-Ts), and eEF2 (similar to EF-G). The elongation factors and their respective roles in the process differ between bacteria and eukaryotes, although the overall process is similar.

Termination Process Comparison

Termination occurs when a stop codon is encountered, signaling the release of the completed polypeptide chain. Both bacteria and eukaryotes employ release factors (RFs) to recognize stop codons and catalyze the release of the polypeptide. However, there are differences in the release factors used: bacteria use RF1 and RF2 for stop codon recognition and RF3 for release, whereas eukaryotes use a single release factor eRF1 for recognition and eRF3 for release. In conclusion, while the translation process is similar and highly conserved between bacteria and eukaryotes, there are notable differences in ribosome structure, translation initiation, elongation factors, and termination between the two domains of life.