Proteins are high molecular weight organic substances that are composed of alpha amino acids that are connected by a peptide bond in a single chain. Their main function is regulatory. And about what and how it manifests itself, now should be told in detail.
Process description
Proteins have the ability to receive and transmit information. This is due to their implementation of the regulation of processes occurring in cells and throughout the body as a whole.
This action is reversible, and usually requires the presence of a ligand. So, in turn, is called a chemical compound that forms a complex with biomolecules, and subsequently produces certain effects (pharmacological, physiological or biochemical).
Interestingly, scientists regularly discover new regulatory proteins. It is assumed that today only a small part of them is known.
Proteins that perform a regulatory function are divided into varieties. And about each of them is worth telling separately.
Functional classification
It is pretty arbitrary. After all, one hormone can perform a variety of tasks. But in general, the regulatory function ensures the advancement of the cell along its cycle, further transcription, translation, splicing and activity of other protein compounds.
Everything happens due to binding to other molecules or due to enzymatic action. By the way, these substances play a very important role. After all, enzymes, being complex molecules, accelerate chemical reactions in a living organism. And some of them inhibit the activity of other proteins.
But now we can proceed to the study of species classification.
Hormone proteins
They affect various physiological processes and directly on the metabolism. Hormone proteins are formed in the endocrine glands, after which they are carried by the blood in order to transmit an information signal.
They spread randomly. However, they act exclusively on those cells that have specific receptor proteins. Only hormones can contact them.
As a rule, slow processes are regulated by hormones. These include the development of the body and the growth of individual tissues. But there are exceptions.
Such is adrenaline - a derivative of amino acids, the main hormone of the adrenal medulla. Its allocation provokes the impact of a nerve impulse. The heartbeat becomes more frequent, blood pressure rises, other responses occur. It affects the liver - it provokes the breakdown of glycogen. As a result, glucose is released into the blood, and the brain with muscles uses it as an energy source.
Receptor proteins
They also have a regulatory function. The human body is, in fact, a complex system that constantly receives signals from the external and internal environment. This principle is observed in the work of its constituent cells.
So, for example, membrane receptor proteins transmit a signal from the surface of a structurally elementary unit inward, simultaneously transforming it. They regulate cellular functions by binding to a ligand located on the receptor outside the cell. What happens in the end? Another protein inside the cell is activated.
It is worth noting one important nuance. The vast majority of hormones affect the cell only if there is a specific receptor on its membrane. It may be a glycoprotein or another protein.
An example is the β2-adrenergic receptor. It is located on the membrane of the liver cells. If stress occurs, then an adrenaline molecule binds to it, as a result of which the β2-adrenoreceptor is activated. What happens next? An already activated receptor activates the G-protein, which subsequently attaches GTP. After many intermediate steps, glycogen phosphorolysis occurs.
What is the conclusion? The receptor carried out the first signaling action, which led to glycogen breakdown. It turns out that without it, subsequent reactions taking place inside the cell would not have occurred.
Protein-regulating transcription
Another topic that needs to be addressed. In biology, there is the concept of a transcription factor. This is the name of proteins, which also have an inherent regulatory function. It consists in controlling the process of mRNA synthesis on a DNA template. This is called transcription - the transfer of genetic information.
What can be said about this factor? Protein performs a regulatory function either independently or in conjunction with other elements. The result is a decrease or increase in the binding constant of RNA polymerase with sequences of the regulated gene.
Transcription factors have a defining feature - the presence in the composition of one or more DNA domains interacting with specific DNA sites. This is important to know. Indeed, other proteins also involved in the regulation of gene expression lack DNA domains. This means that they cannot be attributed to transcription factors.
Protein kinase
Talking about what elements perform a regulatory function in cells, these substances should also be noted. Protein kinases are enzymes that modify other proteins by phosphorylation of amino acid residues with hydroxyl groups in the composition (these are tyrosine, threonine and serine).
What is this process? During phosphorylation, the function of the substrate usually changes or is modified. The enzyme activity, by the way, can also change, as well as the position of the protein in the cell itself. Interesting fact! It is estimated that about 30% of proteins can be modified using protein kinases.
And their chemical activity can be traced in the cleavage of the phosphate group from ATP and in the subsequent covalent addition to the residue of any amino acid. Thus, protein kinases have a strong effect on cellular life. If their work is disrupted, then various pathologies can develop, even some types of cancer.
Protein Phosphatases
Continuing to study the features and examples of regulatory function, you should pay attention to these proteins. The action carried out by protein phosphatases is the removal of phosphate groups.
What does it mean? In simple terms, these elements perform dephosphorylation, a process opposite to that which occurs as a result of exposure to protein kinases.
Splicing regulation
It also cannot be ignored. Splicing is a process in which some nucleotide sequences are removed from RNA molecules, and then sequences that are stored in a "mature" molecule are joined.
What does it have to do with the topic being studied? There are regions within eukaryotic genes that do not encode amino acids. They are called their introns. First, they correspond during transcription onto pre-mRNA, after which a special enzyme “cuts them out”.
Only those proteins that are enzymatically active participate in splicing. Only they are able to impart the desired conformation of prem-RNA.
By the way, there is still the concept of alternative splicing. This is a very interesting process. The proteins involved in it prevent the excision of some nitrons, but at the same time contribute to the removal of others.
Carbohydrate metabolism
The regulatory function in the body is performed by many organs, systems and tissues. But, since we are talking about proteins, then the role of carbohydrates, which are also important organic compounds, is also worth talking about.
This is a very detailed topic. Carbohydrate metabolism as a whole represents a huge number of enzymatic reactions. And one of the possibilities of its regulation is the conversion of enzyme activity. It is achieved due to the functioning molecules of a particular enzyme. Or as a result of biosynthesis of new ones.
We can say that the regulatory function of carbohydrates is based on the principle of feedback. First, the excess substrate that enters the cell provokes the synthesis of new enzyme molecules, and then their biosynthesis is inhibited (after all, the accumulation of metabolic products leads to this).
Regulation of fat metabolism
This is the last thing. Since protein and carbohydrates have been said, fats need to be mentioned.
The process of their metabolism is closely related to carbohydrate. If the concentration of glucose in the blood rises, then the breakdown of triglycerides (fats) decreases, as a result of which their synthesis is activated. Reducing its amount, on the contrary, has a braking effect. As a result, fat breakdown is enhanced and accelerated.
A simple and logical conclusion follows from all this. The relationship between carbohydrate and fat metabolism is aimed at only one thing - to meet the energy needs experienced by the body.