Concanavalin A
Encyclopedia
Concanavalin A is a lectin
(carbohydrate
-binding protein
) originally extracted from the jack-bean, Canavalia ensiformis
. It binds specifically to certain structures found in various sugar
s, glycoprotein
s, and glycolipid
s, mainly internal and nonreducing terminal α-D-mannosyl
and α-D-glucosyl groups. ConA is a plant mitogen, and is known for its ability to stimulate mouse T-cell subsets giving rise to four functionally distinct T cell populations, including precursors to suppressor T-cell; one subset of human suppressor T-cells as well is sensitive to ConA. ConA was the first lectin to be available on a commercial basis, and is widely used in biology
and biochemistry
to characterize glycoprotein
s and other sugar-containing entities on the surface of various cells. It is also used to purify glycosylated macromolecules in lectin affinity chromatography, as well as to study immune regulation by various immune cells.
: each sub-unit (26.5KDa
, 235 amino-acids, heavily glycated) binds a metallic atom (usually Mn2+ and a Ca2+). Its tertiary structure has been elucidated, and molecular basis of its interactions with metals, its affinity for the mannose and glucose are well known.
ConA binds specifically α-D-mannosyl and α-D-glucosyl residues (two hexoses differing only by the alcohol on carbon 2) in terminal position of ramified structures from B-Glycans (reach in α-mannose, or hybrid and bi-antennary glycanes complexes). It has 4 binding sites, corresponding to the 4 sub-units. The molecular weight is 104-112KDa
and the isoelectric point
(pI) is in the range of 4.5-5.5.
Concanavalin A has a low-frequency wave number of 20 cm−1 in its Raman spectra
. This emission has been assigned to the breathing motion of the beta barrel
consisting of 14 beta-strands in the concanavalin A molecule.
ConA can also initiate cell division (mitogenesis) principally acting on T-lymphocytes, by stimulating the energy metabolism of thymocytes within seconds of exposure.
(CEA). It also interacts with lipoprotein
s.
ConA agglutinates strongly erythrocytes irrespective of blood-groups, and various cancerous cells. It was demonstrated that transformed cells and trypsin-treated normal cells do not agglutinate at 4°C, thereby initiate suggesting that there is a temperature-sensitive step involved in ConA-mediated agglutination.
ConA-mediated agglutination of other cell types has been reported, including muscle
cells (myocytes), B-lymphocyte
s (through surface Immunoglobulins), fibroblast
s, rat thymocyte
s, human fetal (but not adult) intestinal epithelial cells, and adipocyte
s. ConA is a also a lymphocyte
mitogen
.
ConA interacts with the surface mannose
residues of many microbes, like the bacteria E. coli
, and Bacillus subtilis
and the protist Dictyostelium discoideum
.
It has also been shown as a stimulator of several matrix metalloproteinases (MMPs).
ConA has proven useful in applications requiring solid-phase immobilization of glycoenzymes, especially those have proved difficult to immobilize by the traditional covalent coupling. Using ConA-couple matrices, such enzymes may be immobilized in high quantities without a concurrent loss of activity and/or stability. Such noncovalent ConA-glycoenzyme couplings may be relatively easily reversed by competition with sugars or at acidic pH. If necessary for certain applications, these couplings can be converted to covalent bindings by chemical manipulation.
A recent (2009) report from Taiwan demonstrated potent therapeutic effect of ConA against experimental hepatoma (liver cancer); in the study by Lei and Chang, ConA was found to be sequestered more by hepatic tumor cells, in preference to surrounding normal hepatocytes. Internalization of ConA occurs preferentially to the mitochondria after binding to cell membrane glycoproteins, which triggers an autophagic cell death. ConA was found to partially inhibit tumor nodule growth independent of its lymphocyte activation; the eradication of the tumor in the murine in situ hepatoma model in this study was additionally attributed to the mitogenic/lymphoproliferative action of ConA that may have activated a CD8+ T-cell-mediated, as well as NK- and NK-T cell-mediated, immune response in the liver.
Lectin
Lectins are sugar-binding proteins that are highly specific for their sugar moieties. They play a role in biological recognition phenomena involving cells and proteins. For example, some viruses use lectins to attach themselves to the cells of the host organism during infection...
(carbohydrate
Carbohydrate
A carbohydrate is an organic compound with the empirical formula ; that is, consists only of carbon, hydrogen, and oxygen, with a hydrogen:oxygen atom ratio of 2:1 . However, there are exceptions to this. One common example would be deoxyribose, a component of DNA, which has the empirical...
-binding protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
) originally extracted from the jack-bean, Canavalia ensiformis
Canavalia ensiformis
Canavalia ensiformis, or Jack-bean, is a legume which is used for animal fodder and human nutrition, especially in Brazil where it is called feijão-de-porco . It is also the source of concanavalin A.- Description :...
. It binds specifically to certain structures found in various sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
s, glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
s, and glycolipid
Glycolipid
Glycolipids are lipids with a carbohydrate attached. Their role is to provide energy and also serve as markers for cellular recognition.-Metabolism:...
s, mainly internal and nonreducing terminal α-D-mannosyl
Mannose
Mannose is a sugar monomer of the aldohexose series of carbohydrates. Mannose is a C-2 epimer of glucose. It is not part of human metabolism, but is a component of microbial cell walls, and is therefore a target of the immune system and also of antibiotics....
and α-D-glucosyl groups. ConA is a plant mitogen, and is known for its ability to stimulate mouse T-cell subsets giving rise to four functionally distinct T cell populations, including precursors to suppressor T-cell; one subset of human suppressor T-cells as well is sensitive to ConA. ConA was the first lectin to be available on a commercial basis, and is widely used in biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
and biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
to characterize glycoprotein
Glycoprotein
Glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. In proteins that have segments extending...
s and other sugar-containing entities on the surface of various cells. It is also used to purify glycosylated macromolecules in lectin affinity chromatography, as well as to study immune regulation by various immune cells.
Structure and properties
As most lectins, the ConA is a homotetramerTetramer
A tetramer is a protein with four subunits . There are homotetramers such as glutathione S-transferase or single-strand binding protein, dimers of hetero-dimers such as hemoglobin , and heterotetramers, where each subunit is different.-Subunit interactions in tetramers:The interactions between...
: each sub-unit (26.5KDa
KDA
KDA may refer to:* Karachi Development Authority* Kongsberg Defence & Aerospace* Kotelawala Defence Academy* Kramer Design Associates* Lithium diisopropylamide, KDA is the potassium analogue of lithium diisopropylamideOr kDa may refer to:...
, 235 amino-acids, heavily glycated) binds a metallic atom (usually Mn2+ and a Ca2+). Its tertiary structure has been elucidated, and molecular basis of its interactions with metals, its affinity for the mannose and glucose are well known.
ConA binds specifically α-D-mannosyl and α-D-glucosyl residues (two hexoses differing only by the alcohol on carbon 2) in terminal position of ramified structures from B-Glycans (reach in α-mannose, or hybrid and bi-antennary glycanes complexes). It has 4 binding sites, corresponding to the 4 sub-units. The molecular weight is 104-112KDa
KDA
KDA may refer to:* Karachi Development Authority* Kongsberg Defence & Aerospace* Kotelawala Defence Academy* Kramer Design Associates* Lithium diisopropylamide, KDA is the potassium analogue of lithium diisopropylamideOr kDa may refer to:...
and the isoelectric point
Isoelectric point
The isoelectric point , sometimes abbreviated to IEP, is the pH at which a particular molecule or surface carries no net electrical charge....
(pI) is in the range of 4.5-5.5.
Concanavalin A has a low-frequency wave number of 20 cm−1 in its Raman spectra
Raman spectroscopy
Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational, and other low-frequency modes in a system.It relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range...
. This emission has been assigned to the breathing motion of the beta barrel
Beta barrel
A beta barrel is a large beta-sheet that twists and coils to form a closed structure in which the first strand is hydrogen bonded to the last.Beta-strands in beta-barrels are typically arranged in an antiparallel fashion...
consisting of 14 beta-strands in the concanavalin A molecule.
ConA can also initiate cell division (mitogenesis) principally acting on T-lymphocytes, by stimulating the energy metabolism of thymocytes within seconds of exposure.
Biological activity
Concanavalin A interacts with diverse receptors containing mannose carbohydrates, notably rhodopsin, blood group markers, insulin-receptor the Immunoglobulins and the carcino-embryonary antigenCarcinoembryonic antigen
Carcinoembryonic antigen is a glycoprotein involved in cell adhesion. It is normally produced during fetal development, but the production of CEA stops before birth. Therefore, it is not usually present in the blood of healthy adults, although levels are raised in heavy smokers...
(CEA). It also interacts with lipoprotein
Lipoprotein
A lipoprotein is a biochemical assembly that contains both proteins and lipids water-bound to the proteins. Many enzymes, transporters, structural proteins, antigens, adhesins, and toxins are lipoproteins...
s.
ConA agglutinates strongly erythrocytes irrespective of blood-groups, and various cancerous cells. It was demonstrated that transformed cells and trypsin-treated normal cells do not agglutinate at 4°C, thereby initiate suggesting that there is a temperature-sensitive step involved in ConA-mediated agglutination.
ConA-mediated agglutination of other cell types has been reported, including muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
cells (myocytes), B-lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
s (through surface Immunoglobulins), fibroblast
Fibroblast
A fibroblast is a type of cell that synthesizes the extracellular matrix and collagen, the structural framework for animal tissues, and plays a critical role in wound healing...
s, rat thymocyte
Thymocyte
Thymocytes are hematopoietic progenitor cells present in the thymus. Thymopoiesis is the process in the thymus by which thymocytes differentiate into mature T lymphocytes. The primary function of thymocytes is the generation of T lymphocytes . The thymus provides an inductive environment, which...
s, human fetal (but not adult) intestinal epithelial cells, and adipocyte
Adipocyte
However, in some reports and textbooks, the number of fat cell increased in childhood and adolescence. The total number is constant in both obese and lean adult...
s. ConA is a also a lymphocyte
Lymphocyte
A lymphocyte is a type of white blood cell in the vertebrate immune system.Under the microscope, lymphocytes can be divided into large lymphocytes and small lymphocytes. Large granular lymphocytes include natural killer cells...
mitogen
Mitogen
A mitogen is a chemical substance that encourages a cell to commence cell division, triggering mitosis. A mitogen is usually some form of a protein.Mitogenesis is the induction of mitosis, typically via a mitogen....
.
ConA interacts with the surface mannose
Mannose
Mannose is a sugar monomer of the aldohexose series of carbohydrates. Mannose is a C-2 epimer of glucose. It is not part of human metabolism, but is a component of microbial cell walls, and is therefore a target of the immune system and also of antibiotics....
residues of many microbes, like the bacteria E. coli
Escherichia coli
Escherichia coli is a Gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms . Most E. coli strains are harmless, but some serotypes can cause serious food poisoning in humans, and are occasionally responsible for product recalls...
, and Bacillus subtilis
Bacillus subtilis
Bacillus subtilis, known also as the hay bacillus or grass bacillus, is a Gram-positive, catalase-positive bacterium commonly found in soil. A member of the genus Bacillus, B. subtilis is rod-shaped, and has the ability to form a tough, protective endospore, allowing the organism to tolerate...
and the protist Dictyostelium discoideum
Dictyostelium discoideum
Dictyostelium discoideum is a species of soil-living amoeba belonging to the phylum Mycetozoa. D. discoideum, commonly referred to as slime mold, is a eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its lifetime. D...
.
It has also been shown as a stimulator of several matrix metalloproteinases (MMPs).
ConA has proven useful in applications requiring solid-phase immobilization of glycoenzymes, especially those have proved difficult to immobilize by the traditional covalent coupling. Using ConA-couple matrices, such enzymes may be immobilized in high quantities without a concurrent loss of activity and/or stability. Such noncovalent ConA-glycoenzyme couplings may be relatively easily reversed by competition with sugars or at acidic pH. If necessary for certain applications, these couplings can be converted to covalent bindings by chemical manipulation.
A recent (2009) report from Taiwan demonstrated potent therapeutic effect of ConA against experimental hepatoma (liver cancer); in the study by Lei and Chang, ConA was found to be sequestered more by hepatic tumor cells, in preference to surrounding normal hepatocytes. Internalization of ConA occurs preferentially to the mitochondria after binding to cell membrane glycoproteins, which triggers an autophagic cell death. ConA was found to partially inhibit tumor nodule growth independent of its lymphocyte activation; the eradication of the tumor in the murine in situ hepatoma model in this study was additionally attributed to the mitogenic/lymphoproliferative action of ConA that may have activated a CD8+ T-cell-mediated, as well as NK- and NK-T cell-mediated, immune response in the liver.
External links
- Concanavalin A structure
- World of Lectin, Gateway to lectins con A in complex with methyl alpha1-2 mannobioside