Lectins are carbohydrate -binding proteins that are highly specific for sugar groups that are part of other molecules, so cause agglutination of particular cells or precipitation of glycoconjugates and polysaccharides . Lectins have a role in recognition at the cellular and molecular level and play numerous roles in biological recognition phenomena involving cells, carbohydrates, and proteins. Lectins also mediate attachment and binding of bacteria , viruses , and fungi to their intended targets.
31-465: Lectins are found in many foods. Some foods, such as beans and grains, need to be cooked, fermented or sprouted to reduce lectin content. Some lectins are beneficial, such as CLEC11A , which promotes bone growth, while others may be powerful toxins such as ricin . Lectins may be disabled by specific mono- and oligosaccharides , which bind to ingested lectins from grains, legumes, nightshade plants, and dairy; binding can prevent their attachment to
62-561: A slow cooker , will not remove all the lectins. Some studies have found that lectins may interfere with absorption of some minerals, such as calcium , iron , phosphorus , and zinc . The binding of lectins to cells in the digestive tract may disrupt the breakdown and absorption of some nutrients, and as they bind to cells for long periods of time, some theories hold that they may play a role in certain inflammatory conditions such as rheumatoid arthritis and type 1 diabetes , but research supporting claims of long-term health effects in humans
93-480: A deeper understanding of their numerous biological functions, the plant lectins, also known as phytohemagglutinins , were noted for their particularly high specificity for foreign glycoconjugates (e.g., those of fungi and animals) and used in biomedicine for blood cell testing and in biochemistry for fractionation . Although they were first discovered more than 100 years ago in plants, now lectins are known to be present throughout nature. The earliest description of
124-911: A function. Several plant lectins have been found to recognize noncarbohydrate ligands that are primarily hydrophobic in nature, including adenine , auxins , cytokinin , and indole acetic acid , as well as water-soluble porphyrins . These interactions may be physiologically relevant, since some of these molecules function as phytohormones . Lectin receptor kinases (LecRKs) are believed to recognize damage associated molecular patterns (DAMPs), which are created or released from herbivore attack. In Arabidopsis , legume-type LecRKs Clade 1 has 11 LecRK proteins. LecRK-1.8 has been reported to recognize extracellular NAD molecules and LecRK-1.9 has been reported to recognize extracellular ATP molecules. Extraction of proteins and lectins can be extracted via similar processes, also with their analysis, and discovery. For example cottonseed contains compounds of interest within
155-549: A growth factor for primitive hematopoietic progenitor cells . An alternative splice variant has been described but its biological nature has not been determined. This article on a gene on human chromosome 19 is a stub . You can help Misplaced Pages by expanding it . Anterograde labeling method In neuroscience , anterograde tracing is a research method that is used to trace axonal projections from their source (the cell body , or soma ) to their point of termination (the synapse ). A hallmark of anterograde tracing
186-445: A hyperintense signal in T 1 -weighted MRI and thus serves as a contrast agent. Mn enters through voltage dependent calcium channels, is taken into intracellular organelles and is transported by the endogenous neuronal transport system including kinesin-1, accumulating at distant locations. Statistical parametric mapping of Mn accumulation in time-lapse images provides detailed information not only about neuronal circuitry but also about
217-584: A lectin is believed to have been given by Peter Hermann Stillmark in his doctoral thesis presented in 1888 to the University of Dorpat . Stillmark isolated ricin, an extremely toxic hemagglutinin, from seeds of the castor plant ( Ricinus communis ). The first lectin to be purified on a large scale and available on a commercial basis was concanavalin A , which is now the most-used lectin for characterization and purification of sugar-containing molecules and cellular structures. The legume lectins are probably
248-451: A lectin-free diet in his book The Plant Paradox (2017). It excludes a large range of commonplace foods including whole grains , legumes, and most fruit, as well as the nightshade vegetables : tomatoes, potatoes, eggplant, bell peppers, and chili peppers. Gundry's claims about lectins are considered pseudoscience . His book cites studies that have nothing to do with lectins, and some that show—contrary to his own recommendations—that avoiding
279-485: A major family of protein antinutrients , which are specific sugar-binding proteins exhibiting reversible carbohydrate-binding activities. Lectins are similar to antibodies in their ability to agglutinate red blood cells. Many legume seeds have been proven to contain high lectin activity, termed hemagglutination . Soybean is the most important grain legume crop in this category. Its seeds contain high activity of soybean lectins ( soybean agglutinin or SBA). Long before
310-694: Is limited and most existing studies have focused on developing countries where malnutrition may be a factor, or dietary choices are otherwise limited. The first writer to advocate a lectin-free diet was Peter J. D'Adamo, a naturopathic physician best known for promoting the Blood type diet . He argued that lectins may damage a person's blood type by interfering with digestion, food metabolism, hormones, insulin production—and so should be avoided. D'Adamo provided no scientific evidence nor published data for his claims, and his diet has been criticized for making inaccurate statements about biochemistry. Steven Gundry proposed
341-401: Is still uncertain. Once thought to be necessary for rhizobia binding, this proposed function was ruled out through lectin-knockout transgene studies. The large concentration of lectins in plant seeds decreases with growth, and suggests a role in plant germination and perhaps in the seed's survival itself. The binding of glycoproteins on the surface of parasitic cells also is believed to be
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#1732779751286372-448: Is the labeling of the presynaptic and the postsynaptic neuron(s). The crossing of the synaptic cleft is a vital difference between the anterograde tracers and the dye fillers used for morphological reconstruction. The complementary technique is retrograde tracing , which is used to trace neural connections from their termination to their source (i.e. synapse to cell body). Both the anterograde and retrograde tracing techniques are based on
403-582: Is used to trace the path of efferent axons with PHA-L , a lectin from the kidney bean . A lectin ( BanLec ) from bananas inhibits HIV-1 in vitro . Achylectins, isolated from Tachypleus tridentatus , show specific agglutinating activity against human A-type erythrocytes. Anti-B agglutinins such as anti-BCJ and anti-BLD separated from Charybdis japonica and Lymantria dispar , respectively, are of value both in routine blood grouping and research. Lectins from legume plants, such as PHA or concanavalin A , have been used widely as model systems to understand
434-465: The Paramyxoviridae family, use this mechanism to bind and gain entry to target cells. Purified lectins are important in a clinical setting because they are used for blood typing . Some of the glycolipids and glycoproteins on an individual's red blood cells can be identified by lectins. Non blood-group antigens can be identified by lectins: In neuroscience, the anterograde labeling method
465-461: The brain . These molecules are absorbed locally by the soma (cell body) of various neurons and transported to the axon terminals , or they are absorbed by axons and transported to the soma of the neuron. Other tracer molecules allow for the visualization of large networks of axonal projections extending from the neurons exposed to the tracer. Over the recent years viral vectors have been developed and implemented as anterograde tracers to identify
496-419: The optical pathway : by injecting the virus into the eye, the pathway from the retina into the brain was visualized. Viral tracers use a receptor on the host cell to attach to it and are then endocytosed . For example, HSV uses the nectin receptor and is then endocytosed. After endocytosis, the low pH inside the vesicle strips the envelope of the virion after which the virus is ready to be transported to
527-462: The carbohydrates within the cell membrane. The selectivity of lectins means that they are useful for analyzing blood type , and they have been researched for potential use in genetically engineered crops to transfer pest resistance. branched α-mannosidic structures (high α-mannose type, or hybrid type and biantennary complex type N-Glycans) R2-GlcNAcβ1-4(Fucα1-6)GlcNAc-R1 William C. Boyd alone and then together with Elizabeth Shapleigh introduced
558-480: The cell body. It was shown that pH and endocytosis are crucial for the HSV to infect a cell. Transport of the viral particles along the axon was shown to depend on the microtubular cytoskeleton . There is also a group of tracers that consist of protein products that can be taken up by the cell and transported across the synapse into the next cell. Wheat-germ agglutinin (WGA) and Phaseolus vulgaris leucoagglutinin are
589-503: The development of pest. Concanavalin A and other commercially available lectins have been used widely in affinity chromatography for purifying glycoproteins. In general, proteins may be characterized with respect to glycoforms and carbohydrate structure by means of affinity chromatography , blotting , affinity electrophoresis , and affinity immunoelectrophoreis with lectins, as well as in microarrays , as in evanescent -field fluorescence-assisted lectin microarray. One example of
620-418: The dynamics of transport within them, and the location of distal connections. This approach provides information about circuitry throughout the brain in living animals. (see also Viral neuronal tracing ) In order to trace projections from a specific region or cell, a genetic construct, virus or protein can be locally injected, after which it is allowed to be transported anterogradely. Viral tracers can cross
651-401: The molecular basis of how proteins recognize carbohydrates, because they are relatively easy to obtain and have a wide variety of sugar specificities. The many crystal structures of legume lectins have led to a detailed insight of the atomic interactions between carbohydrates and proteins. Legume seed lectins have been studied for their insecticidal potential and have shown harmful effects for
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#1732779751286682-459: The most well known tracers, however they are not strict anterograde tracers: especially WGA is known to be transported anterogradely as well as retrogradely. WGA enters the cell by binding to oligosaccharides , and is then taken up via endocytosis via a caveolae-dependent pathway. Other anterograde tracers widely used in neuroanatomy are the biotinylated dextran amines (BDA), also used in retrograde tracing . The anterograde tracing technique
713-557: The most well-studied lectins. CLEC11A 6320 20256 ENSG00000105472 ENSMUSG00000004473 Q9Y240 O88200 NM_002975 NM_009131 NP_002966 NP_033157 C-type lectin domain family 11 member A is a protein that in humans is encoded by the CLEC11A gene . This gene encodes a member of the C-type lectin superfamily. The encoded protein is a secreted sulfated glycoprotein and functions as
744-558: The powerful biological attributes of lectins is the biochemical warfare agent ricin. The protein ricin is isolated from seeds of the castor oil plant and comprises two protein domains . Abrin from the jequirity pea is similar: Lectins are widespread in nature, and many foods contain the proteins. Some lectins can be harmful if poorly cooked or consumed in great quantities. They are most potent when raw as boiling, stewing or soaking in water for several hours can render most lectins inactive. Cooking raw beans at low heat, though, such as in
775-554: The studies of extraction and purification of proteins Some hepatitis C viral glycoproteins may attach to C-type lectins on the host cell surface (liver cells) to initiate infection. To avoid clearance from the body by the innate immune system , pathogens (e.g., virus particles and bacteria that infect human cells) often express surface lectins known as adhesins and hemagglutinins that bind to tissue-specific glycans on host cell-surface glycoproteins and glycolipids . Multiple viruses, including influenza and several viruses in
806-459: The synapse, and can be used to trace connectivity between brain regions across many synapses. Examples of viruses used for anterograde tracing are described by Kuypers. Most well known are the herpes simplex virus type1 (HSV) and the rhabdoviruses . HSV was used to trace the connections between the brain and the stomach, in order to examine the brain areas involved in viscero-sensory processing. Another study used HSV type1 and type2 to investigate
837-490: The target neurons in the brain. Much of what is currently known about connectional neuroanatomy was discovered through the use of the anterograde and retrograde tracing techniques. Several methods exist to trace projections originating from the soma towards their target areas. These techniques initially relied upon the direct physical injection of various visualizable tracer molecules (e.g. green fluorescent protein , lipophylic dyes or radioactively tagged amino acids ) into
868-465: The target regions of projecting neurons. Alternatively strategies are transsynaptic anterograde tracers, which can cross the synaptic cleft, labeling multiple neurons within a pathway. Those can also be genetic or molecular tracers. Recently manganese-enhanced magnetic resonance imaging (MEMRI) has been used to trace functional circuits in living brains, as pioneered by Russ Jacobs, Robia Paultler, Alan Koretsky and Elaine Bearer . The Mn ion gives
899-529: The term "lectin" in 1954 from the Latin word lectus , "chosen" (from the verb legere , to choose or pick out). Lectins may bind to a soluble carbohydrate or to a carbohydrate moiety that is a part of a glycoprotein or glycolipid . They typically agglutinate certain animal cells and/or precipitate glycoconjugates . Most lectins do not possess enzymatic activity. Lectins have these functions in animals: The function of lectins in plants ( legume lectin )
930-406: The visualization of the biological process of axonal transport . The anterograde and retrograde tracing techniques allow the detailed descriptions of neuronal projections from a single neuron or a defined population of neurons to their various targets throughout the nervous system . These techniques allow the "mapping" of connections between neurons in a particular structure (e.g. the eye ) and
961-506: The whole grains wheat , barley , and rye will allow increase of harmful bacteria while diminishing helpful bacteria. Lectins are one of many toxic constituents of many raw plants that are inactivated by proper processing and preparation (e.g., cooking with heat, fermentation). For example, raw kidney beans naturally contain toxic levels of lectin (e.g. phytohaemagglutinin ). Adverse effects may include nutritional deficiencies , and immune ( allergic ) reactions. Lectins are considered