The myosin molecule and cardiac function

1. The structure is different.

Myosin: Consists of one or two heavy chains and several light chains. In general, myosin is made up of three domains: the motor domain, the neck, and the tail.

Actin: Cellular actin comes in two forms: a monomeric globule called G-actin and a polymer filament called F-actin (i.e., a filament composed of many g-actin monomers).

2. The nature is different.

Myosin: Myosin is a globulin class, insoluble in water and soluble in KCl or NaCl solution. It has enzymatic activity, and by interacting with actin, it hydrolyzes the terminal phosphate group of ATP, and can also hydrolyze GTP, CTP, etc., converting chemical energy into mechanical energy, thus producing various forms of movement.

Actin: Actin is a globular protein with a molecular weight of about 42,000 to 48,000 and a molecular diameter of about 5 nanometers. An actin molecule binds to an adenosine triphosphate molecule.

Globular actin can be associated with fibrillary actin. The latter two strands are twisted together to form a skeleton, and then embedded with tropomyosin and troponin, that is, the filaments of myofibrils in the muscle.

3. The functions are different.

Myosin: Myosin, as the molecular motor of the cytoskeleton, is a multifunctional protein whose main function is to provide force for muscle contraction.

Actin: Actin forms filaments ('F-actin'or microfilaments), which are essential elements of the eukaryotic cytoskeleton and are able to undergo very rapid polymerization and depolymerization kinetics.

The upstairs is too complicated, and the simple thing is that myoglobin is the protein produced by the cleavage of muscle tissue after injury, and hemoglobin is the product of the breakdown of blood cells, especially red blood cells.

Both substances can clog the tubules of the kidneys, causing damage to kidney function.

Thick myomefilaments are made up of myosin molecules, and thin myomefilaments are made up of actin, tropomyosin, and troponin.

Ca2+ binds to troponin, exposing the binding site on actin and making contact with the myosin head, myosin hydrolyzes ATP to release energy, while the myosin head undergoes flexion motion, pulling actin towards the M-line, causing the thin muscle filaments to slide between the thick muscle filaments.

To summarize, proteins have the following main functions:

1.Catalytic function Enzymes in living organisms are made up of proteins, which are catalysts for the metabolism of organisms. Without enzymes, various chemical reactions in living organisms cannot proceed properly. For example, without amylase, starch cannot be broken down and utilized.

2.Structural function Proteins can be used as structural components of living organisms. In higher animals, collagen is the main extracellular structural protein involved in connective tissue and bone as a scaffold for the body, accounting for 1 4 of the total protein.

The lamellar structures in cells, such as cell membranes, mitochondria, chloroplasts, and endoplasmic reticulum, are made up of insoluble proteins and lipids. Animal hair and nails are made of keratin.

3.Transport function Hemoglobin in vertebrate red blood cells and hemocyanin in invertebrates play a role in transporting oxygen during respiration. Apolipoproteins in the blood transport fats, and transferrin transports iron.

Some fat-soluble hormones also require proteins for transport, such as thyroxine, which binds to thyroxine-binding globulin in order to be transported in the bloodstream.

4.Storage function The role of some proteins is to store amino acids as nutrients for organisms and raw materials for the growth and development of embryos or young children. Such proteins include ovalbumin in eggs, casein in milk, and gliadin in wheat seeds.

Ferritin in the liver stores excess iron in the blood for use in times of iron deficiency.

5.Motor function Myosin and actin in muscles are essential components of the locomotor system, and their conformational changes cause muscle contractions and drive the body to move. The flagellin in bacteria has a similar effect in that its contraction causes the flagella to wobble, which allows the bacteria to swim in the water.

6.Defensive function The immune response of higher animals is a defensive function of the body, which is also mainly achieved through proteins (antibodies). Protein factors, lysozyme, and interferons of the coagulation and fibrinolytic systems also play a role in defense and protection.

7.Regulatory function Certain hormones, all hormone receptors, and many other regulators are proteins.

8.Messaging Functions Proteins are also inseparable from the messaging process in living organisms. For example, rhodopsin is required for the transmission of visual information, and taste proteins are required for taste perception. Rhodopsin in rod cells can be excited with just 1 photon to produce vision.

9.Genetic Regulatory Function Both the storage and expression of genetic information are related to proteins. DNA is entangled in proteins (histones) when stored.

Some proteins, such as repressors, are involved in the expression of specific genes. The expression of the galactosidase gene is inhibited by a repressor protein, which can only be expressed by derepression when galactosidase needs to be synthesized.

10.Other functions Some organisms can synthesize toxic proteins for attack or self-defense. For example, some plants produce a toxic protein after being bitten by insects. Diphtheria toxin inhibits biological protein synthesis.

The functions are different due to the different combinations of amino acids in their proteins. It mainly has the following functions:

Catalytic function Proteins with catalytic functions are called enzymes, and all the chemical reactions of the metabolism of organisms are catalyzed by enzymes.

Motor function From the lowest bacterial flagellar movements to the muscle contractions of higher animals, it is achieved through proteins. The relaxation and contraction of muscles are mainly done by the thick filaments with myosin as the main component and the filaments with actin as the main component sliding against each other.

Transport function In the process of life activities, the transport of many small molecules and ions is completed by various specific proteins. For example, plasma albumin transports small molecules in blood, and hemoglobin in red blood cells transports oxygen and carbon dioxide.

Mechanical support and protection function The tissues with mechanical support functions of higher animals, such as bones, connective tissues, hair, nails, etc., which have covering protective functions, are mainly composed of collagen, keratin, elastin, etc.

Immunity and defense In order to maintain their own survival, organisms have many types of defenses, many of which are carried out by proteins. For example, antibodies are a class of highly specific proteins that recognize and bind foreign substances that invade organisms, such as allogeneic proteins, viruses and bacteria, and cancel their harmful effects.

Regulatory function Polypeptides and protein hormones play an extremely important role in various processes such as the regulation of metabolic function, the control of growth and differentiation, the regulation of reproductive function and the continuation of species in maintaining the normal life activities of organisms. In addition, there are proteins that receive and transmit regulatory information, such as receptor proteins for various hormones.

The development of proteins, as biological macromolecules that play an important role in life activities, is closely related to all major research topics that uncover the mysteries of life. Protein is the main food component of humans and other animals, and a high-protein diet is one of the important signs of the improvement of people's living standards. Many pure protein preparations are also effective drugs, such as insulin, human gamma globulin, and some enzyme preparations.

In terms of clinical examination, the determination of enzyme activity and changes in certain proteins can be used as indicators for the clinical diagnosis of some diseases, such as the identification of lactate dehydrogenase isoenzyme can be used as an indicator of myocardial infarction, and the elevation of alpha-fetoprotein can be used as an indicator of early liver cancer lesions. In industrial production, certain proteins are important raw materials for the food industry and light industry, such as wool and silk are proteins, and leather is treated collagen. After applying various enzyme preparations in industrial sectors such as tanning, pharmaceutical, and silk reeling, production efficiency and product quality can be improved.

The importance of protein in agriculture, animal husbandry, and aquaculture is also obvious.

The protein may be used as a reagent for screening compounds or salts that can promote or inhibit the activity of the protein of the present invention. Furthermore, this compound or its salts and neutralizing antibodies that inhibit the protein activity of the present invention can be used as ** or drugs for the prevention of bronchial asthma, chronic obstructive pulmonary disease, etc.

Functional proteins have different functions depending on their structure.

First, the role is different.

1. Myosin: It plays an important role in the movement of cells and the transport of substances in cells.

2. Actin: It plays an important role in the movement and contraction of cells, and plays an important role in muscle movement.

Second, the existence of different locations.

1. Myosin: found in smooth muscle.

2. Actin: It is found in the filaments of myofibrils of striated muscles, and also in smooth muscle.

Third, the structure is different.

1. Myosin: composed of one or two heavy chains and several light chains; It is composed of three domains: the motor domain, the neck and the tail.

2. Actin: Each actin molecule is composed of adenosine triphosphate (ATP) or adenosine diphosphate (ADP) molecule.