An Overview of Structure, Formation and Function of Ribosome

Posted by beauty33 on March 24th, 2020

Ribosomes are factories that synthesize proteins in cells. In a vigorously growing bacterium, there are about 20,000 ribosomes, whose proteins account for 10% of total cellular proteins, and RNA accounts for 80% of total cellular RNA. Each ribosome can translate 40 codons in one second to form 40 amino acid peptide bonds, and its peptide synthesis efficiency is extremely high. It can be seen that the ribosome is an assembly machine for peptide chains.

The structure

The ribosome contains 40% protein and 60% RNA. The protein combines with RNA in a certain order to form two ribosomal subunits. Among them, RNAs are backbone structures. Some proteins do not directly bind to RNA, but bind to others. Proteins, rRNAs, and other cofactors in the ribosome together provide all the enzyme activities required for translation. These enzyme activities are only available in the presence of the overall structure of the ribosome.

The formation

Ribosomes from different sources have slightly different shapes, sizes, and chemical compositions. They are generally divided into two types, 70S and 80S, according to different sedimentation coefficients. 70S ribosomes are found in bacteria, mitochondria and chloroplasts, and 80S ribosomes are found in eukaryotes. In the cytoplasm of organisms.

All ribosomes are composed of two large and small subunits, and the large and small subunits of the ribosome are combined only when the protein is synthesized using the mRNA as a template-the mRNA should first bind to the free small ribosome subunit, then after binding to the large subunit and generating a certain peptide, due to the membrane localization signals of the peptide and the ribosomal subunit, it is determined whether it will continue to synthesize in the free state in the cytoplasm or combine it with the rough endoplasmic reticulum to synthesize the peptide chain. After the synthesis is terminated, the large and small subunits dissociate again and are free in the cytoplasmic matrix.

The separation of ribosomal size subunits is related to the Mg2 + ion concentration in the cytosol. Studies have found that when the Mg2 + concentration in the cytosol is less than 1 mmol / l, the ribosome of 70S is easily dissociated into two subunits of 50S and 30S; and when the Mg2 + concentration in the cytosol is greater than 10 mmol / l, the two ribosomes often The dimers that form 100S are in the normal ribosome structure in between.

The rRNA-encoding DNA fragment is called rRNA gene. It is a repeated multi-copy gene. There are about 200 copies in a human cell. rDNA has no histone core and is a naked DNA segment. There is a non-transcribed spacer DNA between two adjacent genes. During transcription, the RNA polymerase is arranged along the DNA molecule. This enzyme moves from the head of the gene to the end. The transcribed rRNA molecule protrudes from the polymerase, the closer the end is, the longer it is, and it can extend from the left and right sides.

The function

When it comes to the main functions of ribosomes, they assume the role of bringing together amino acids to form particular proteins, which are important for completing the cell's activities.

The other functions include:

1. The procedure of creation of proteins, the deoxyribonucleic acid makes mRNA by the step of DNA transcription.
2. The hereditary information from the mRNA is converted into proteins amid DNA translation.
3. The arrangements of protein assembly amid protein synthesis are indicated in the mRNA.
4. The mRNA is arranged in the nucleus and is moved to the cytoplasm for an additional operation of protein synthesis.
5. The proteins which are arranged by the ribosomes currently in the cytoplasm are utilized inside the cytoplasm by itself. The proteins created by the bound ribosomes are moved outside the cell.

Taking into consideration their main function in developing proteins, it's clear that a cell can’t function in the absence of ribosomes.

CD genomics provides a ribosome-profiling strategy that is based on the deep sequencing of ribosome-protected mRNA fragments and enables genome-wide investigation of translation with sub cordon resolution. Using nuclease digestion, the ribosome position and the translated message can be precisely determined by analyzing the protected ~30-nt area of the mRNA template.

Application of Ribosome Profiling

1. Sequences of ribosome-protected mRNA.
2. The study of active mRNA translation with sequencing.
3. Prediction of protein abundance.
4. Identify translation start sites
5. Investigation of transcriptional control and post-transcriptional regulation.