The interaction and structure of IRNA, tRNA, RRNA - the three main nucleic acids, is considered by such a science as cytology. It will help to find out what is the role of transport ribonucleic acid (tRNA) in cells. This very small, but at the same time undeniably important molecule takes part in the process of combining the proteins that make up the body.
What is the structure of tRNA? It is very interesting to consider this substance "from the inside", to find out its biochemistry and biological role. And also, how are the structure of tRNA and its role in protein synthesis interrelated?
What is tRNA, how does it work?
Transport ribonucleic acid is involved in the construction of new proteins. Almost 10% of all ribonucleic acids are transport. To make it clear what chemical elements a molecule is formed from, we will describe the structure of the secondary structure of tRNA. Secondary structure considers all major chemical bonds between elements.
This is a macromolecule consisting of a polynucleotide chain. Nitrogenous bases in it are connected by hydrogen bonds. As in DNA, RNA has 4 nitrogenous bases: adenine,cytosine, guanine, and uracil. In these compounds, adenine is always associated with uracil, and guanine, as usual, with cytosine.
Why does a nucleotide have the prefix ribo-? Simply, all linear polymers that have a ribose instead of a pentose at the base of the nucleotide are called ribonucleic. And transfer RNA is one of 3 types of just such a ribonucleic polymer.
Structure of tRNA: biochemistry
Let's look into the deepest layers of the molecular structure. These nucleotides have 3 components:
- Sucrose, ribose is involved in all types of RNA.
- Phosphoric acid.
- Nitrogenous bases. These are purines and pyrimidines.
Nitrogenous bases are interconnected by strong bonds. It is customary to divide bases into purine and pyrimidine.
Purines are adenine and guanine. Adenine corresponds to an adenyl nucleotide of 2 interconnected rings. And guanine corresponds to the same "single-ring" guanine nucleotide.
Pyramidines are cytosine and uracil. Pyrimidines have a single ring structure. There is no thymine in RNA, since it is replaced by an element such as uracil. This is important to understand before looking at other structural features of tRNA.
Types of RNA
As you can see, the structure of TRNA cannot be briefly described. You need to delve into biochemistry to understand the purpose of the molecule and its true structure. What other ribosomal nucleotides are known? There are also matrix or informational and ribosomal nucleic acids. Abbreviated as RNA and RNA. All 3molecules work closely with each other in the cell so that the body receives correctly structured protein globules.
It is impossible to imagine the work of one polymer without the help of 2 others. Structural features of tRNAs become more understandable when viewed in conjunction with functions that are directly related to the work of ribosomes.
The structure of IRNA, tRNA, RRNA is similar in many ways. All have a ribose base. However, their structure and functions are different.
Discovery of nucleic acids
The Swiss Johann Miescher found macromolecules in the cell nucleus in 1868, later called nucleins. The name "nucleins" comes from the word (nucleus) - the nucleus. Although a little later it was found that in unicellular creatures that do not have a nucleus, these substances are also present. In the middle of the 20th century, the Nobel Prize was received for the discovery of the synthesis of nucleic acids.
TRNA functions in protein synthesis
The name itself - transfer RNA speaks of the main function of the molecule. This nucleic acid "brings" with it the essential amino acid required by the ribosomal RNA to make a particular protein.
The tRNA molecule has few functions. The first is the recognition of the IRNA codon, the second function is the delivery of building blocks - amino acids for protein synthesis. Some more experts distinguish the acceptor function. That is, the addition of amino acids according to the covalent principle. An enzyme such as aminocil-tRNA synthatase helps to “attach” this amino acid.
How is the structure of tRNA related to itsfunctions? This special ribonucleic acid is arranged in such a way that on one side of it there are nitrogenous bases, which are always connected in pairs. These are the elements known to us - A, U, C, G. Exactly 3 "letters" or nitrogenous bases make up the anticodon - the reverse set of elements that interacts with the codon according to the principle of complementarity.
This important structural feature of tRNA ensures that there will be no errors when decoding the template nucleic acid. After all, it depends on the exact sequence of amino acids whether the protein that the body needs at the present time is synthesized correctly.
Building features
What are the structural features of tRNA and its biological role? This is a very ancient structure. Its size is somewhere around 73 - 93 nucleotides. The molecular weight of a substance is 25,000–30,000.
The structure of the secondary structure of tRNA can be disassembled by studying the 5 main elements of the molecule. So, this nucleic acid consists of the following elements:
- enzyme contact loop;
- loop for contact with the ribosome;
- anticodon loop;
- acceptor stem;
- the anticodon itself.
And also allocate a small variable loop in the secondary structure. One shoulder in all types of tRNA is the same - a stem of two cytosine and one adenosine residues. It is in this place that the connection with 1 of the 20 available amino acids occurs. Each amino acid has a separate enzyme - its own aminoacyl-tRNA.
All information that encrypts the structure of allnucleic acids are found in DNA itself. The structure of tRNA in all living creatures on the planet is almost identical. It will look like a leaf when viewed in 2-D.
However, if you look in volume, the molecule resembles an L-shaped geometric structure. This is considered the tertiary structure of tRNA. But for the convenience of studying it is customary to visually “untwist”. The tertiary structure is formed as a result of the interaction of elements of the secondary structure, those parts that are mutually complementary.
The tRNA arms or rings play an important role. One arm, for example, is required for chemical bonding with a particular enzyme.
A characteristic feature of a nucleotide is the presence of a huge number of nucleosides. There are more than 60 types of these minor nucleosides.
Structure of tRNA and coding of amino acids
We know that the tRNA anticodon is 3 molecules long. Each anticodon corresponds to a specific, "personal" amino acid. This amino acid is connected to the tRNA molecule using a special enzyme. As soon as the 2 amino acids come together, the bonds to the tRNA are broken. All chemical compounds and enzymes are needed until the required time. This is how the structure and functions of tRNA are interconnected.
There are 61 types of such molecules in the cell. There can be 64 mathematical variations. However, 3 types of tRNA are missing due to the fact that exactly this number of stop codons in the IRNA does not have anticodons.
Interaction of IRNA and TRNA
Let's consider the interaction of a substance with MRNA and RRNA, as well as structural features of TRNA. Structure and purposemacromolecules are interconnected.
The structure of IRNA copies information from a separate section of DNA. DNA itself is too large a connection of molecules, and it never leaves the nucleus. Therefore, an intermediary RNA is needed - informational.
Based on the sequence of molecules copied by the RNA, the ribosome builds a protein. The ribosome is a separate polynucleotide structure, the structure of which needs to be explained.
Ribosomal tRNA interaction
Ribosomal RNA is a huge organelle. Its molecular weight is 1,000,000 - 1,500,000. Almost 80% of the total amount of RNA is ribosomal nucleotides.
It kind of captures the IRNA chain and waits for anticodons that will bring tRNA molecules with them. Ribosomal RNA consists of 2 subunits: small and large.
The ribosome is called the “factory”, because in this organelle all the synthesis of substances necessary for everyday life takes place. It is also a very ancient cell structure.
How does protein synthesis occur in the ribosome?
The structure of tRNA and its role in protein synthesis are interrelated. The anticodon located on one of the sides of the ribonucleic acid is suitable in its form for the main function - the delivery of amino acids to the ribosome, where the gradual alignment of the protein occurs. Essentially, the TRNA acts as an intermediary. Its task is only to bring the necessary amino acid.
When information is read from one part of the IRNA, the ribosome moves further along the chain. The matrix is only needed for transmissionencoded information about the configuration and function of a single protein. Next, another tRNA approaches the ribosome with its nitrogenous bases. It also decodes the next part of the RNC.
Decoding occurs as follows. Nitrogenous bases combine according to the principle of complementarity in the same way as in DNA itself. Accordingly, TRNA sees where it needs to "moor" and to which "hangar" to send the amino acid.
Then in the ribosome, the amino acids selected in this way are chemically bound, step by step a new linear macromolecule is formed, which, after the end of synthesis, twists into a globule (ball). Used tRNAs and IRNAs, having fulfilled their function, are removed from the protein "factory".
When the first part of the codon connects to the anticodon, the reading frame is determined. Subsequently, if for some reason a frame shift occurs, then some sign of the protein will be rejected. The ribosome cannot intervene in this process and solve the problem. Only after the process is completed, the 2 rRNA subunits are combined again. On average, for every 104 amino acids, there is 1 error. For every 25 proteins already assembled, at least 1 replication error is sure to occur.
TRNA as relic molecules
Since tRNA may have existed at the time of the origin of life on earth, it is called a relic molecule. It is believed that RNA is the first structure that existed before DNA and then evolved. The RNA World Hypothesis - formulated in 1986 by laureate W alter Gilbert. However, to proveit's still difficult. The theory is defended by obvious facts - tRNA molecules are able to store blocks of information and somehow implement this information, that is, do work.
But opponents of the theory argue that a short life span of a substance cannot guarantee that tRNA is a good carrier of any biological information. These nucleotides are rapidly degraded. The lifetime of tRNA in human cells ranges from several minutes to several hours. Some species can last up to a day. And if we talk about the same nucleotides in bacteria, then the terms are much shorter - up to several hours. In addition, the structure and functions of tRNA are too complex for a molecule to become the primary element of the Earth's biosphere.
