Translation-Important Points

Translation-Protein Biosynthesis

Translation is the process of Synthesis of Proteins and involves many steps.
First we will discuss some key concepts about the Biosynthesis of Proteins, then we will learn the actual process.
These Important points must be understood first to fully understand the Translation.

There are 4 main steps involved:

Correct pairing of codon with the anti codon of the tRNA is essential

The process translates the 3-letter alphabet of nucleotide sequences on mRNA into the 20-letter alphabet of amino acids that make the proteins.
The mRNA is translated from its 5’end to its 3’ end, producing a protein synthesized from it N-terminal end to its C-terminal end
Prokaryotic mRNAs are Polycistronic.
Each coding region has its own Initiation & Termination codon and,
Produces a separate species of polypeptides.
In contrast, each Eukaryotic mRNA has only one coding region-Monocistronic.

In a first step, the AA reacts with ATP to form an aminoacyl- AMP-
enzyme complex.
PPi is released & hydrolyzed by pyrophosphatase.
The second step comprises the transfer of the activated AA to the 3′ end of tRNA
The specificity of the aminoacyl-tRNA synthetase allows it to recognize not only the AA but also the tRNA corresponding to that amino acid
There are enzymes, specific for each amino acid

The aminoacyl–tRNA complex is directed toward the site of synthesis,
Where the loaded tRNA, mRNA, ribosomes & factors that initiate the assembly of the chain gather.

Protein synthesis occurs by peptide bond formation between successive amino acids whose order is specified by a gene and thus by an mRNA.
There is formation of a peptide bond between the carboxyl group on one amino acid & the amino group of another.
The amino acids are attached to the 3′ ends of their respective tRNAs.
The aminoacyl–tRNAs are situated in the P & A sites of the ribosome.
Proteins are synthesized from the Amino to the Carboxyl terminus.

Translation occurs in the cytoplasm of both Prokaryotic and Eukaryotic cells.
In Prokaryotes, ribosomes can begin translating the mRNA even before RNA polymerase completes its transcription.
In Eukaryotes, translation and transcription are completely separated in time and space with transcription in the nucleus and translation in the cytoplasm.