What is the protein synthesis process?

2022-07-27 0 By

Ribosomal Protein synthesis Ribosomal binding site Protein structure Amino acid proteins are important components of living organisms. Protein synthesis is the linking of amino acids into polypeptide chains according to the sequence specified by the nucleotide sequence of the mRNA transcript.Protein synthesis What are the main components of protein synthesis?Ribosomes are large molecular complexes composed of ribosomal RNA (rRNA) and many ribosomal proteins, which are molecular machines that facilitate protein synthesis.Amino acids are brought to the ribosome by transfer RNA (tRNA).The codons of mRNA, most of which contain complementary codons to match, form the different amino acid molecules called the basis of protein formation.In this process, each ribosome is made up of two subunits with different functions that must be brought together for protein synthesis.The small (40 S) subunit binds tO the mRNA and contains sites where the tRNA anticodon matches the complementary mRNA sequence.The large (60 S) subunit contains sites for forming peptide bonds between amino acids carried by tRNA to the ribosome, resulting in polypeptide chains that subsequently fold to form the final protein structure.MRNA it can be associated with a single complete (80 S) ribosome, called a monomer, or translated simultaneously by multiple ribosomes in structures called polyribosomes.Once the ribosome reaches a termination codon with no matching tRNA, the translation terminates and the ribosomal subunit dissociates and is recycled for another round of translation.What is the process of ribosomal protein synthesis?The protein synthesis process can be simply divided into three steps: translation, transcription and termination.Ribosomes play an important role in translation with mRNA and tRNA.When a single ribosome binds to an mRNA, it is called a monomer;When multiple ribosomes are attached to an mRNA chain at the same time, a chain-like structure is formed, which is called multiple ribosomes.As shown in the figure below: C (left) translation inhibitors EIF4EBP1-3 and PDCD4 can prevent eIF4E and eIF4A from binding to eIF4G scaffold protein respectively.(Middle) Schematic diagram of eIF4F binding to mRNA.(right) Schematic diagram of preinitiation complex Protein synthesis There are three main steps in the translation of aN mRNA sequence into a protein: translation initiation, elongation, and termination.The key to protein synthesis is translation initiation.In RNA polymerase II mediated transcription, all mammalian mrnas are labeled with methylguanosine caps at their 5′ ends.Cap structures are essential for binding proteins that control translation initiation by recruiting mRNA to the ribosome or inhibit translation by preventing ribosome interactions.Most mrnas in mammalian cells are translated by the eIF4F complex, which is a heterotrimer composed of the proteins eIF4E, eIF4G, and eIF4A.As shown in Figure 1c, eIF4E binds to the mRNA cap to recruit mRNA for translation.Many mrnas have secondary structures in their 5′ untranslated region (UTR).When eIF4A binds to eIF4G, it mediates the unfolding of these secondary structures through its RNA helicase activity, which is enhanced by eIF4B and eIF4H.EIF4G acts as a scaffold protein, enhancing eIF4A activity and bringing eIF4E-binding mRNA to the preinitiation complex (PIC).PIC contains a small ribosomal subunit and a range of other translation initiation factors, including GTP-bound eIF2, which mediates initiation of tRNA binding.EIF4G also recruits a polyadenylate binding protein, which interacts with the 3′ mRNA terminal to allow cyclization of the transcript and enhance protein translation.Once recruited, the PIC scans the mRNA for translation start sites, as indicated by the AUG codon that encodes the amino acid methionine.Once the start codon is recognized and paired with a methionine-containing tRNA, eIF2-GTP hydrolyzes and dissociates from the PIC to form a large ribosome.At this point, protein elongation begins.Termination codons are triplet base sequences on mRNA that determine, respectively, the initiation and termination of protein translation.