Hello guys, Today we are discussing one of the interesting field from the field of biology. There are several researches are carried out by many scientist. Which main component in build our body. That is today’s topic is Protein synthesis from DNA. Protein synthesis is a one of the interesting and most important mechanism. So let’s what is protein synthesis in detail ? And also steps of protein synthesis ?
What are protein ?
Proteins are the main building blocks of body. Proteins are nothing but the long chain of amino acids. Mechanism for Protein synthesis required DNA, 3 types of RNA i.e m-RNA, r-RNA, t-RNA. And the most important thing is that the code for synthesis of protein is built on DNA, which called as genes. Every single gene produce single protein. That is One gene – one protein.
Why protein synthesis ?
So guys, first most important it useful to carry metabolic activities in living cell. Along with that it decides phenotypic expression of living cell from biochemical reactions. And these biochemical reaction require one of the type of enzyme. As as we know that every enzyme is protein. Also for structure of cell thousands of catalytic proteins are required. After that functional proteins like harmones are also plays most important role metabolism.
What are steps of protein synthesis from DNA ?
So friends, after looking overall information about protein, and why they are essential ? Now we are going to discuss next part i.e What is the mechanism of synthesis of protein ? Or we can say, what are steps of protein synthesis ? So let’s see…
First step of protein synthesis is transcription, so what is transcription ? Generally in simple way it is process of getting genetic code for protein synthesis from DNA. And also it is the process of formation of m-RNA from DNA. So how it is carried out ?
- The process of transcription is carried out in the presence of an enzyme called DNA dependent RNA Polymerase.
- First to create RNA it needs a promoter, structural gene and a terminator.
- Then the template strand i.e DNA strand which is used for synthesis Protein or RNA. This strand is also called as antisence strand.
- This strand is oriented in the direction 3′ to 5′.
- And other than that another strand of DNA which is not involved in RNA synthesis is called as coding strand or sense strand. And this orients from 5′ to 3′.
- As I told earlier, that it requires promoter that is nothing but the a small sequence of DNA which provides binding site for promoter. And it presents towards 5′ end. Also another small DNA sequence present at 5′ end called terminator.
- Structural gene is generally monocistronic i.e. only one gene codes on a single m-RNA in eukaryotes. And polycistronic in prokaryotes i.e. many genes on single m-RNA.
- Then this gene gets transcribed. In eukaryotes, there are two parts i.e. intron and exon
Formation of hn-RNA
Generally, Intron is a unessential part of gene. Which do not coded any code. And that of Extron iessential which coded any particular protein.
- Now, in transcription the enzyme RNA polymerase binds to the promoter site. As result two strands of DNA get separate.
- After that, for formation of RNA, complementary base pairs are collected from surrounding. And these are attached to form long chain of RNA, and this process is known as Elongation.
- In this process a small part of RNA and the enzyme RNA polymerase are remains attached to DNA. And when it reaches to terminator region it falls down.
- And here is the end of the transcription process and we get newly formed RNA.
After forming RNA it has to complete another several steps to complete whole process in eukaryotes. And in prokaryotes it doesn’t require. So in eukaryotes three types of RNA Polymerase are help to complete it. These are RNA Polymerase I, RNA Polymerase II, RNA Polymerase III
- First, RNA Polymerase I forms r-RNA.
- Second, RNA Polymerase lI forms hn-RNA.
- Third, RNA Polymerase lII forms t-RNA.
Formation of m-RNA
hn-RNA is the hetronucleor RNA. And the RNA without splicing, Capping and Telling is known as hn-RNA. After complete these three steps we call it as m-RNA.
hn-RNA is not active or we can mature so to become it active it has to complete these steps ( splicing, Capping and Telling ) and this results formation of m-RNA.
- Splicing : this is a process where removing of introns from RNA takes place.
- Capping : it is the process where methyl guanosine triphosphate add at 5′ end of RNA or hn-RNA.
- Telling : in this process long chain of adenylate forms.
After that this results m-RNA. And this m-RNA further go to cytoplasm from nucleus to complete process of Protein synthesis. Or it goes for process of translation.
In the process of translation, the code or script present on RNA in the form of nucleotides. And this code read by ribosomes. And with the help of t-RNA it forms Protein. So let’s see what is it ?
- So when first m-RNA enter in cytoplasm the ribosomes which are present in cytoplasm attach to m-RNA. For reading code.
- This code is read by ribosomes in triplets or codon. And it decides particular amino acid.
For example here is the table you can see :
Initiation of protein synthesis :
During the Protein synthesis or translation process following activity occurs.
- In this process it require m-RNA having codons, two sub units of ribosomes i.e 30s and 50s sub units. And also AA-t- RNA ( aminoacyl-tRNA ) complex.
AA-t-RNA is the t-RNA where it having amino acids or we can say it is complex formed by amino acid and t-RNA.
- After that, it also require initiation factor.
- And generally in prokaryotes, the initiation factor is or first amino acid is,N-formal-methionine ( f-met ). And methionine ( met ) in eukaryotes.
- Now, the process start with binding 30s subunit of ribosome to m-RNA & also 50s subunit. And this forms 70s complex of ribosome.
This ribosome is with 3 sides. Generally aminoacyl site (A), Peptide site (P) and Exit site (E).
- Aminoacyl site (A) : It is a site from where the AA-t-RNA complex enter with amino acid to form polypeptide chain.
- Peptidyl site (P) : From the this site, the formed peptide chain or the long chain of amino acid realeses.
- Exit site (E) : through this site the empty t-RNA i.e without amino acid are released through this site.
- After that, as the first codon of m-RNA is always AUG or GUG. The first amino acid i.e. met or f-met are attaches and the next process start we call it as Elongation.
After the end of the process of elongation starts and performs following activity :
- This is nothing but formation peptide chain, or processing long chain of amino acid.
- This process is catalyzed under a enzyme named as peptidyl transferase.
- Every t-RNA complex brings a single amino acid. And place it as per combination of codon and anticodon.
- Like wise the ribosome moves along m-RNA in the direction of 5′ to 3′. And this movement of ribosome is called as translocation.
- After that there is the end of elongation process and start termination process.
- The elongation process is carried out till last amino acid is added by t-RNA.
- And it stopes or termination start when it reaches to nonsense codgon or termination codon i.e. UAA,UAG or UGA.
- Also the factor R1, R2, and S are help in identify stop codons which reasults it release polypeptide chain.
- And after that subunits of ribosomes (30s & 50s) are get free from m-RNA.
at the end with the help of ATP & GTP the peptide chain is transferred to protein. And here is the end of protein synthesis.
So guys looking the overall mechanism of protein synthesis, I want to say another time that is WOW.
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