5 Significant Stages of Protein Synthesis

Proteins are a major component of the body systems, including all transport, defense, and communication mechanisms. The cells synthesize proteins as per the needs. Researchers can synthesize the proteins they need in E. coli. DNA contains information that dictates the structure of the proteins a cell makes to suit the functions.

Scientists use DNA and RNA to fight viruses. Genetic information undergoes replication to target the virus DNA and disable its functionality. But the whole process requires the synthesis and use of certain proteins. We have covered the whole process of protein synthesis. The key steps will guide you when working on new protein synthesis projects in your lab.

1. Amino Acids Activation

The activation of amino acids is the step when adenosine triphosphate supplies them with energy. Aminoacyl-tRNA synthetase enzyme is required to enhance the activation process. The enzyme, in both class I and II, catalyzes the binding process of amino acids to the transport ribonucleic acid.

With the help of the enzyme, amino acids attach to the α-phosphate of ATP. During the process, a pyrophosphate is released by the acceptor. The reaction ensures that there is a negative energy change, which facilitates the forward movement of the process. In the next stage, the enzyme accelerates the transfer of amino acid to the ribose of the tRNA. This step generates an activated aminoacyl-tRNA.

Each aminoacyl-tRNA synthetase has a distinct recognition of the tRNA and the amino acid to bind. Therefore, synthetase has to determine the correct amino acid for a particular tRNA before releasing aminoacyl-tRNA. This is the only way to ensure that the amino acids bind with the correct tRNA.

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The amino acids need genetic information to form specific types of proteins. During the activation of amino acids, DNA information also copies to RNA strands ready for binding with the amino acids. The first step is the transcription, where messenger ribonucleic acid forms. The formation complements the source DNA. Transcription has three stages.

The initiation process is the first stage of transcription. RNA polymerase enzyme binds to the promoter part of a gene. The binding causes the DNA in question to unwind, putting the two strands apart. After unwinding, the enzyme reads the genetic information from one of the strands – which is called a sense strand. RNA polymerase then begins forming an mRNA strand with complementary information to what it reads on the DNA sense strand.

After the initiation process, the enzyme starts what we call the elongation process. Elongation simply means the addition of nucleotides to the newly-formed mRNA. The enzyme moves along

the DNA strand in the 5′ to 3′ direction. As it moves, it translates the code in groups of three (codons) and adds their complementary to the mRNA as it moves forward, making the new strand longer.

After writing enough information to the mRNA, the process stops. We call it the termination – which marks the end of the transcription process. This happens when the polyadenylation signal appears. It informs the enzyme that it has reached where the mRNA string should end. Then the strand detaches from the DNA strand, allowing it to rewind.

3. Processing of the mRNA

Single-celled organisms, like the amoeba, move to translation immediately after transcription. They can also start translating the genetic material while transcription is still in progress. This is because the direction of translation follows that of transcription, and the new mRNA needs no further processing.

However, in eukaryotes, the cell nucleus has a membrane that separates it from the other parts of the cell. Newly-formed messenger ribonucleic acid strands need to go through a “processing” stage before they leave the nucleus. During the processing, some modifications may take place to protect the mRNA. That is when it becomes “mature” for the next step.

Editing of mRNA changes the nucleotides to form variations of the corresponding proteins. The editing may add a stop to mRNA earlier, making it shorter. This example is seen in the APOB proteins in humans. Splicing ensures that only encoding parts (exons) are on the mRNA strand. All the introns are cut off the strand.

Polyadenylation is the most important part of mRNA processing. Here, the strand receives a “tail” of adenine bases. Apart from marking the end of the strand, the tail also protects the messenger ribonucleic acid from the enzymes that could break it down.

4. RNA Translation

The translation is the “main” part of protein expression and purification. This is the stage where RNA molecules are translated into proteins. After leaving the cell nucleus, the mRNA goes to the ribosome. Here, already there are various types of proteins and ribosomal ribonucleic acid. rRNA is essential in protein synthesis. It reads the genetic material of the arriving mRNA and the amino acids as they arrive with the tRNA.

Various tRNA structures carry different types of amino acids. They, therefore, have to arrive in the correct sequence when binding with the mRNA. With the help of rRNA, the tRNA surrenders the amino acid. Amino acid molecules then bond together to form a polypeptide chain, which grows until it reaches a stop codon.

5. Processing of the Proteins

Each stop codon marks the end of the protein chain. But the proteins need to be processed before they move to various parts of the body to perform their duties. Some polypeptide chains interact with their amino acids to form folded shapes while others bind with other molecules like lipids ready for transportation.

A majority of the synthesized proteins move to the cytoplasm and enter the Golgi apparatus. Here, further processing occurs. Modifications of the proteins in the Golgi apparatus prepare the proteins for their specific work within the body.

Summing Up

Protein synthesis is a complex process that takes place within the cells. The proteins formed rely on genetic information to ensure that they can perform the tasks they are meant to. Genetic material prevents the synthesis of incompatible proteins or foreign material. The complete process differs depending on the organism’s structure.

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