Question

Identify the following by describing their functions: EF-G, EF-Tu, EF-Ts, EF-P, and peptidyl transferase.

Short answer

EF-G moves the ribosome; EF-Tu delivers aminoacyl-tRNA; EF-Ts regenerates EF-Tu; EF-P aids in peptide bond formation; Peptidyl transferase forms peptide bonds.

Step-by-step solution

Identify EF-G

EF-G (Elongation Factor G) is a protein involved in the translocation step during the elongation cycle of protein synthesis in bacteria. It facilitates the movement of the ribosome along the mRNA after peptide bond formation.

Identify EF-Tu

EF-Tu (Elongation Factor Tu) binds to aminoacyl-tRNA and GTP. It delivers the aminoacyl-tRNA to the A-site of the ribosome during translation. After the correct codon-anticodon pairing, GTP is hydrolyzed and EF-Tu-GDP is released.

Identify EF-Ts

EF-Ts (Elongation Factor Ts) functions as a guanine nucleotide exchange factor. It regenerates EF-Tu by replacing the GDP on EF-Tu with GTP, thereby preparing EF-Tu for another cycle of delivering aminoacyl-tRNA to the ribosome.

Identify EF-P

EF-P (Elongation Factor P) is required for the efficient synthesis of certain proteins. It helps stabilize the formation of the first peptide bond and alleviates ribosomal stalling during the translation of polyproline sequences.

Identify Peptidyl Transferase

Peptidyl transferase is an enzymatic activity found in the ribosome, specifically in the large subunit. It catalyzes the formation of peptide bonds between adjacent amino acids during the synthesis of a protein.

Key concepts

EF-G

Elongation Factor G (EF-G) plays a crucial role during the translocation step in the elongation cycle of protein synthesis in bacteria. EF-G promotes the movement of the ribosome along mRNA after the peptide bond is formed between amino acids. Essentially, EF-G facilitates the ribosome's shift so that the A (aminoacyl) site becomes the new P (peptidyl) site, allowing the ribosome to continue translating the mRNA.

Without EF-G's action, the ribosome would stall, and protein synthesis would be interrupted.

EF-Tu

Elongation Factor Tu (EF-Tu) is essential for the delivery of aminoacyl-tRNA to the ribosome during translation. EF-Tu binds to aminoacyl-tRNA and GTP, forming a complex that transports the tRNA to the A-site of the ribosome.

• Once proper codon-anticodon pairing occurs, the ribosome triggers GTP hydrolysis.
• This results in the release of EF-Tu-GDP from the tRNA, enabling it to engage in the next elongation cycle.
• EF-Tu ensures that only correctly paired tRNAs proceed, maintaining the accuracy of protein synthesis.

EF-Ts

Elongation Factor Ts (EF-Ts) acts as a guanine nucleotide exchange factor for EF-Tu. After EF-Tu releases GDP following tRNA delivery to the ribosome, EF-Ts facilitates the exchange of GDP for GTP on EF-Tu.

This regeneration process is crucial as it preps EF-Tu for another round of tRNA delivery. EF-Ts ensures the continuous availability of active EF-Tu-GTP, thereby sustaining the efficiency of protein elongation.

EF-P

Elongation Factor P (EF-P) assists in the synthesis of proteins, particularly those containing consecutive proline residues. EF-P stabilizes the formation of the first peptide bond, which is a challenging step in protein synthesis.

EF-P also helps in alleviating ribosomal stalling during the translation of polyproline sequences. By doing so, EF-P ensures the smooth manufacturing of proteins that would otherwise suffer from translation interruptions.

Peptidyl Transferase

Peptidyl transferase is a vital enzymatic activity found within the large subunit of the ribosome. This enzyme catalyzes the formation of peptide bonds between adjacent amino acids.

• The peptide bond formation marks a critical step in the elongation phase of protein synthesis.
• Peptidyl transferase ensures that amino acids linked to the tRNA in the P-site are joined to the incoming amino acids in the A-site.
It's a key player in building the growing polypeptide chain during translation.

Elongation Factors

Elongation factors, including EF-G, EF-Tu, EF-Ts, and EF-P, are proteins that greatly facilitate the elongation phase of protein synthesis.

These factors work collectively to ensure the accuracy and efficiency of translating mRNA into a polypeptide chain. They assist in:

• transporting aminoacyl-tRNA to the ribosome
• translocating the ribosome along mRNA
• regenerating themselves for repeated use
• resolving any stalls that occur during translation.

Each factor has a unique role that contributes to the smooth progression of protein synthesis.

Ribosome Function

Ribosomes are the molecular machines responsible for protein synthesis. They translate the genetic information encoded in mRNA to form proteins.

Ribosomes consist of two subunits: large and small.

• The small subunit reads the mRNA.
• The large subunit forms peptide bonds with its peptidyl transferase activity.

Ribosomes use various elongation factors to assist in each step of translation, from decoding mRNA to peptide bond formation and translocation. Their proper function is essential for the accurate and efficient synthesis of proteins within the cell.