Name: how protein synthesis ends
Uploaded: 2023-04-30T18:28:45.000Z
Duration: 1 min 44 s
Channel: JoVE
Description: Protein synthesis ends when translation reaches a stop signal on the mRNA. At this stage, the ribosome no longer adds amino acids to the growing polypeptide chain. Instead, the process shifts to releasing the completed protein.

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.5

Termination of Translation

Once an mRNA is translated, the ribosome needs to dissociate from the RNA and release the newly made polypeptide chain.&#160;
Translation is terminated when a stop codon, UAA, UAG, or UGA, is encountered. There are no complementary tRNAs that correspond to stop codons.
Instead, when a stop codon is positioned on the A site of the ribosome, it is recognized by proteins called release factors, RF1 or RF2.
This binding forces the enzyme peptidyl transferase in the ribosome to catalyze the addition of a water molecule instead of an amino acid to the peptidyl-tRNA.
As a result, the P-site amino acid detaches from its tRNA, releasing the newly made polypeptide into the cytoplasm.&#160;
Next, a third release factor, RF3, bound to GDP joins the ribosome.
On the ribosome, RF3 replaces GDP with GTP. This exchange brings about a conformational change in RF3, which triggers the dissociation of RF1 and RF2 from the ribosome.
Then, RF3 catalyzes GTP hydrolysis, which allows the ribosomal subunits to dissociate from each other and from the mRNA.
The disassembled ribosomal subunits bound to an initiator tRNA, can now join a new mRNA for another round of translation.

termination of translation

The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the site where the peptide bond is formed - and a large, internal, water-filled tube through which the nascent polypeptide moves. This latter structure is called the Peptide Exit Tunnel, and it begins at the PTC and spans the body of the large ribosomal subunit. During translation, as the nascent polypeptide chain is synthesized, it passes through the peptide exit tunnel. It then emerges out in the solvent side, where the peptide chain is subsequently folded into a protein.
This tunnel formed by the 23S ribosomal RNA creates a large hydrophilic surface, containing tiny hydrophobic patches. The dimensions of the tunnel (approximately 10 nm &#215; 1.5 nm) can accommodate growing, unstructured polypeptide chains, as well as solvent molecules. The interior of the peptide exit tunnel is not complementary to any peptide. Hence, the polypeptide chain does not &#8220;stick&#8221; to the walls and can easily slide through. Once it reaches a location in the exit tunnel where there is sufficient space, the nascent peptide chain starts to fold and may successfully form some &#945;-helical regions. However, the majority of protein folding occurs once the polypeptide exits the ribosome.

The large ribosomal subunit has several important structures essential to translation. These include the peptidyl transferase center (PTC) - which is the ...

Education

JoVE Core

Cell Biology

Unit 1

Translation: RNA to Protein

KEY TERMS AND CONCEPTS

how protein synthesis ends

Protein synthesis ends when translation reaches a stop signal on the mRNA. At this stage, the ribosome no longer adds amino acids to the growing polypeptide chain. Instead, the process shifts to releasing the completed protein.

How Protein Synthesis Ends

translation

How Cells Build Proteins from mRNA

Translation is the cell process that builds proteins from messenger RNA, or mRNA. It comes after transcription and is the final step in gene expression. Ribosomes, which are made of protein and specialized RNA, carry out this process with help from transfer RNA, or tRNA, and other proteins. The result is a chain of amino acids called a polypeptide. Proteins are called the building blocks of life because they make up much of an organism, from muscle fibers and hair to parts of the immune system.

ribosomes

Ribosomes in Protein Synthesis

Ribosomes build proteins by reading messenger RNA, or mRNA, and turning that genetic code into an amino acid chain. Both prokaryotic and eukaryotic cells have ribosomes. Cells that make large amounts of protein, such as secretory cells in the human pancreas, can contain millions of them. Ribosomes are made of ribosomal RNA, or rRNA, and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus, a region of the nucleus that specializes in making ribosomes. There, rRNA joins with...

trna activation

Charging tRNA for Protein Synthesis

tRNA charging is the step that prepares transfer RNA for protein synthesis. In this process, an amino acid is attached to its matching tRNA by an enzyme called aminoacyl-tRNA synthetase. The charged tRNA can then deliver that amino acid during translation. tRNA charging is a key part of how cells build proteins from genetic information. The transcript focuses on the activation of tRNA and the role of aminoacyl-tRNA synthetases in this process. These enzymes help ensure that the correct amino...

initiation of translation

Translation Begins with Ribosome Assembly

Translation begins when a ribosome assembles on an mRNA molecule and starts reading its code. During this first stage of protein synthesis, the cell prepares the machinery needed to build a protein from amino acids. The small ribosomal subunit binds to the mRNA first. It helps position the message so the ribosome can find the correct start site. Then the initiator tRNA, which carries the first amino acid, pairs with the start codon on the mRNA. After the start codon is matched, the large...

Protein synthesis ends when translation reaches a stop signal on the mRNA. At this stage, the ribosome no longer adds amino acids to the growing polypeptide chain. Instead, the process shifts to releasing the completed protein.

improving translational accuracy

Boosting Protein Translation Fidelity

Protein translation fidelity helps cells build the right protein from an mRNA message. The ribosome must read each codon correctly and add the matching amino acid in order. Even small errors can change the final protein. The transcript explains how accuracy can be improved during translation. It focuses on the steps that help the ribosome choose the correct tRNA and keep the growing peptide chain on track. These controls reduce mistakes while the protein is being made. This topic is important...

nonsense-mediated mrna decay

Nonsense-Mediated mRNA Decay and UPF Proteins

Nonsense-mediated mRNA decay is a cell quality-control process that removes faulty mRNA before it can make a shortened protein. It helps protect cells from errors during gene expression. The pathway depends on UPF proteins, which help identify and trigger the breakdown of the problem message. This process matters when an mRNA contains a premature stop signal, also called a nonsense codon. Instead of allowing translation to continue, the cell recognizes the defective message and targets it for...

molecular chaperones and protein folding

Chaperones Guide Protein Folding

Molecular chaperones help proteins fold into the correct shape. Protein folding is a key step after a protein is made, because shape affects function. If a protein does not fold properly, it may not work as it should. Chaperones do not become part of the final protein. Instead, they assist the folding process and help proteins avoid harmful misfolding. They are especially important when newly made proteins are still fragile and need support as they take on their proper structure. This topic...

the proteasome

Protein Recycling by the Proteasome

The proteasome breaks down proteins inside cells. It helps control which proteins stay active and which are removed. This process is an important part of protein recycling. Proteins can be tagged for destruction before they enter the proteasome. The cell uses this system to remove proteins that are no longer needed or that must be cleared away. The proteasome then cuts them into smaller pieces. This protein breakdown helps the cell stay organized and function properly. By clearing selected...

regulated protein degradation

How Cells Remove Unneeded Proteins

Cells remove unneeded proteins through regulated protein degradation. This process helps control which proteins stay active and which proteins are broken down. Protein degradation is not random. The cell uses signals to mark proteins for removal at the right time. This regulation lets the cell respond to changing needs and keep protein levels balanced. Regulated protein degradation is an important part of molecular biology. It shows how cells maintain control over their internal processes by...

proteins: from genes to degradation

Protein Synthesis and Breakdown

Proteins are made from genes and later broken down when they are no longer needed. This page follows that path from gene information to protein degradation, or protein breakdown. It shows how cells build proteins and how they remove them at the right time. The process begins with genes, which carry the instructions for making proteins. Those instructions are used to produce proteins with specific jobs in the cell. After a protein has done its work, the cell can degrade it instead of keeping it...

key terms and concepts

Learn how translation ends at a stop codon, how the ribosome releases the polypeptide chain, and why this final step matters in protein synthesis.

How Protein Synthesis Ends | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Louisiana Student Standards for Science

High School

Life Sciences

From Molecules To Organisms: Structures And Processes

HS-LS1-1

Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.d

Minnesota Academic Standards in Science

Life Science

3.2.1 9L.3.2.1.1

Alabama Course of Study Science

From Molecules to Organisms: Structures and Processes

9-12.B.1.2

Florida Department of Education

SC.912.L.16

SC.912.L.16.5

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

B-LS1-1.

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How Protein Synthesis Ends

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