An Overview of Protein Synthesis


The process of producing proteins is called protein synthesis. The process occurs inside the cell in biological systems. It occurs within the cytoplasm of prokaryotes. In eukaryotes, the coding sequence of the DNA is first converted into a transcript (mRNA) in the nucleus. After leaving the nucleus, the transcript travels to the ribosomes, which are translated into a protein molecule with a specified amino acid sequence.

Protein synthesis is the process through which cells produce proteins using DNA, RNA, and several enzymes. It often involves transcription, translation, and post-translational processes like protein folding, modifications, and proteolysis.

Protein Synthesis Steps

The main steps in protein synthesis are:

  • Transcription
  • Translation
  • Post-translation

Transcription: DNA to RNA

The first part of the fundamental principle of molecular biology is the transcription (DNA → RNA). It involves the transmission of genetic information from DNA to mRNA. An mRNA strand is created during transcription to complement a strand of DNA.

With the aid of the enzyme RNA polymerase, an mRNA template is transcribed from DNA with the protein sequence encoded as a trinucleotide code. This template is subsequently used for translation.

Transcription, like DNA replication, proceeds in the 5′ → 3′ direction. However, it does not require a primer to initiate the process, unlike DNA replication.

Initiation, elongation, and termination are the three stages of transcription.

  • Initiation is the start of transcription. It begins when the RNA polymerase enzyme attaches to the promoter of a gene. The enzyme is prepared to create an mRNA strand with a complementary base sequence. This tells the DNA to unfold so the enzyme may “read” the bases in a specific DNA strand.
  • The process of elongation involves adding nucleotides to the produced mRNA strand.
  • Termination is the conclusion of transcription. RNA polymerase separates from DNA when it transcribes the terminator. This stage marks the end of the mRNA strand.

Translation: RNA to Protein

The second part of the fundamental principle of molecular biology is the translation: RNA → Protein. It is the process by which the genetic code contained in mRNA is read to produce a protein. When mRNA exits the nucleus, it travels to a ribosome composed of proteins and rRNA. The appropriate amino acids are delivered to the ribosome by tRNA molecules, which read the codon sequences in the mRNA.

There are four stages:

  • Activation: The amino acid is covalently linked to the tRNA.
  • Initiation: With the aid of initiation factors, the small subunit of the ribosome attaches to the 5′ end of the mRNA.
  • Elongation: The next aminoacyl-tRNA in line attaches to the ribosome, along with an elongation factor and GTP.
  • Termination: The site A of the ribosome encounters a stop codon.

Post-translation Steps

Protein folding and proteolysis occur after the synthesis of proteins. Protein cleavage by proteases is referred to as proteolysis. It allows the polypeptide to remove its N-terminal, C-terminal, or interior amino acid residues.

A polypeptide chain may go through further steps once it is produced. It might, for example, develop a folded structure due to connections between its amino acids. Additionally, it might be associated with other polypeptides or other substances, such as lipids or carbohydrates. Many proteins move to the Golgi apparatus in the cytoplasm to be transformed for the specific function they will perform.

Protein Synthesis and Misconceptions

Protein synthesis does not produce amino acids. Amino acids are employed as the building blocks for proteins; however, they are not produced during translation. Some students believe that the production of amino acids is the primary goal of protein synthesis.

Not all mutations result in significant or unfavourable changes. When people learn the term “mutation,” they often assume that it means they may get a disease or become deformed. Mutations create genetic diversity, so while some are detrimental, the majority are undetectable, and many are also beneficial.

Stay tuned to BYJU’S Biology for more information.