Question

EF-Tu, a member of the G-protein family, plays a crucial role in the elongation process of translation. Suppose that a slowly hydrolyzable analog of GTP were added to an elongating system. What would be the effect on the rate of protein synthesis?

Short answer

The rate of protein synthesis would decrease.

Step-by-step solution

Understanding EF-Tu's Role

EF-Tu is a G-protein that facilitates the binding of aminoacyl-tRNA to the ribosome during protein synthesis. It requires GTP to function and typically dissociates once GTP is hydrolyzed to GDP.

Consider the Impact of a Slowly Hydrolyzable Analog of GTP

A slowly hydrolyzable GTP analog would bind EF-Tu, but impede the rate of GTP hydrolysis. This would slow down the release of EF-Tu from the ribosome after delivering the aminoacyl-tRNA, subsequently slowing the overall elongation cycle.

Relating to the Rate of Protein Synthesis

Since the elongation process relies on the quick cycle of EF-Tu binding, functioning, and release, introducing a slowly hydrolyzable GTP analog would slow these cycles down, ultimately decreasing the rate of protein synthesis.

Key concepts

EF-Tu's Role in Translation Elongation

EF-Tu is a type of protein known as a G-protein, crucial for the elongation phase of translation in protein synthesis. Its main job is to help deliver aminoacyl-tRNA to the ribosome. Aminoacyl-tRNA is the "delivery truck" carrying amino acids to be added to a growing protein chain.
To do its job, EF-Tu binds to aminoacyl-tRNA in a GTP-bound form. This binding ensures the correct amino acid is added to the chain. Once EF-Tu brings the aminoacyl-tRNA to the ribosome, GTP is hydrolyzed to GDP. This hydrolysis allows EF-Tu to release the aminoacyl-tRNA and exit the ribosome, ready for the next cycle.

Understanding G-proteins

G-proteins, short for guanine nucleotide-binding proteins, are a family of proteins involved in transmitting signals and securing proper cellular functions. They act like switches turned on or off by the binding and hydrolysis of GTP.
In their GTP-bound form, G-proteins are active and able to perform their specific functions. For EF-Tu, this means binding and delivering aminoacyl-tRNA to the ribosome. When GTP is hydrolyzed to GDP, they become inactive, resulting in EF-Tu releasing from the ribosome, to repeat its function. This process ensures efficiency and accuracy during protein synthesis.

• Active state: GTP-bound
• Inactive state: GDP-bound

The Importance of Aminoacyl-tRNA

Aminoacyl-tRNA is a complex that plays an essential role during protein synthesis by carrying the appropriate amino acids to the ribosome. Each aminoacyl-tRNA is specific to one amino acid, ensuring proteins are constructed correctly with the right sequence.
When EF-Tu binds to aminoacyl-tRNA, it ensures that the amino acids are accurately delivered to the ribosome's A-site. The ribosome then helps form a peptide bond between the newly delivered amino acid and the growing peptide chain. Ensuring the correct delivery and attachment is critical for accurate protein synthesis.

GTP Hydrolysis in the Elongation Cycle

GTP hydrolysis is a chemical reaction where GTP loses one of its phosphate groups and is transformed into GDP. This reaction is crucial in the elongation cycle of protein synthesis, providing the energy needed for EF-Tu to release the aminoacyl-tRNA.
The speed of GTP hydrolysis directly impacts the rate of protein synthesis. Quick hydrolysis ensures EF-Tu rapidly releases from the ribosome, making the elongation processes swift and efficient. Conversely, a slow hydrolysis means EF-Tu stays attached longer, delaying further cycles and slowing down the overall protein synthesis rate.

• Purpose: Provides energy for biological processes
• Result: Transforming GTP to GDP
• Impact: Affects speed of protein synthesis