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Kaliotoxin
Kaliotoxin (KTX) inhibits potassium flux through the Kv1.3 voltage-gated potassium channel and calcium-activated potassium channels by physically blocking the channel-entrance and inducing a conformational change in the K+- selectivity filter of the channel. Sources KTX is a neurotoxin derived from the scorpion Androctonus mauretanicus mauretanicus, which is found in the Middle East and North Africa. Chemistry Kaliotoxin is a 4-kDa polypeptide chain, containing 38 amino acids. The formula is . The sequence has a large homology with iberiotoxin from ''Buthus tumulus'', charybdotoxin from ''Leiurus quinquestriatus'' and noxiustoxin from ''Centruroides noxius''. An Important site of the toxin is the K27 side chain (a lysine at place 27 of the protein sequence), which enters the pore and protrudes into the selectivity filter of the channel. Target KTX binds to the Kv1.3 voltage-gated potassium channel and the Calcium-activated potassium channels ( BK channels). These channels co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage-gated Potassium Channel
Voltage-gated potassium channels (VGKCs) are potassium channel, transmembrane channels specific for potassium and Voltage-gated ion channel, sensitive to voltage changes in the cell's membrane potential. During action potentials, they play a crucial role in returning the depolarized cell to a resting state. Classification Alpha subunits Alpha subunits form the actual conductance pore. Based on sequence homology of the hydrophobic transmembrane cores, the alpha subunits of voltage-gated potassium channels are grouped into 12 classes. These are labeled Kvα1-12. The following is a list of the 40 known human voltage-gated potassium channel alpha subunits grouped first according to function and then subgrouped according to the Kv sequence homology classification scheme: Delayed rectifier slowly inactivating or non-inactivating *Kvα1.x - shaker superfamily of potassium channels, Shaker-related: Kv1.1 (KCNA1), Kv1.2 (KCNA2), Kv1.3 (KCNA3), Kv1.5 (KCNA5), Kv1.6 (KCNA6), Kv1.7 (KCN ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charybdotoxin
Charybdotoxin (ChTX) is a 37 amino acid neurotoxin from the venom of the scorpion '' Leiurus quinquestriatus hebraeus'' (''deathstalker'') that blocks calcium-activated potassium channels. This blockade causes hyperexcitability of the nervous system. It is a close homologue of agitoxin and both toxins come from ''Leiurus quinquestriatus hebraeus''. It is named after Charybdis, a sea monster from Greek myth. Chemical properties Family The Charybdotoxin family of scorpion toxins is a group of small peptides that has many family members, such as the pandinotoxin, derived from the venom of scorpion Pandinus imperator. Structure Scorpions such as the deathstalker paralyze their prey by injecting a potent mix of peptide toxins. Charybdotoxin, a 37 amino acid, 4 kDa neurotoxin with the molecular formula C176H277N57O55S7, is one of the peptide toxins that can be extracted from the venom of the scorpion. Its structure is very similar to that of margatoxin. Charybdotoxin contains thre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KcsA Potassium Channel
KcsA (K channel of streptomyces A) is a prokaryotic potassium channel from the soil bacterium ''Streptomyces lividans'' that has been studied extensively in ion channel research. The pH activated protein possesses two transmembrane segments and a highly selective pore region, responsible for the gating and shuttling of K+ ions out of the cell. The amino acid sequence found in the selectivity filter of KcsA is highly conserved among both prokaryotic and eukaryotic K+ voltage channels; as a result, research on KcsA has provided important structural and mechanistic insight on the molecular basis for K+ ion selection and conduction. As one of the most studied ion channels to this day, KcsA is a template for research on K+ channel function and its elucidated structure underlies computational modeling of channel dynamics for both prokaryotic and eukaryotic species. History KcsA was the first potassium ion channel to be characterized using x-ray crystallography by Roderick MacKinn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic
In chemistry, hydrophobicity is the chemical property of a molecule (called a hydrophobe) that is seemingly repelled from a mass of water. In contrast, hydrophiles are attracted to water. Hydrophobic molecules tend to be nonpolar and, thus, prefer other neutral molecules and nonpolar solvents. Because water molecules are polar, hydrophobes do not dissolve well among them. Hydrophobic molecules in water often cluster together, forming micelles. Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. The term ''hydrophobic''—which comes from the Ancient Greek (), "having a fear of water", constructed Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glycine
Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (GGU, GGC, GGA, GGG). Glycine disrupts the formation of alpha-helices in secondary protein structure. Its small side chain causes it to favor random coils instead. Glycine is also an inhibitory neurotransmitter – interference with its release within the spinal cord (such as during a '' Clostridium tetani'' infection) can cause spastic paralysis due to uninhibited muscle contraction. It is the only achiral proteinogenic amino acid. It can fit into both hydrophilic and hydrophobic environments, due to its minimal side chain of only one hydrogen atom. History and etymology Glycine was discovered in 1820 by French chemist Henri Braconnot when he hydrolyzed gelatin by boiling it with sulfuric acid. He originally called it "sugar of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smooth Muscle
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It can be divided into two subgroups, ''single-unit'' and ''multi-unit'' smooth muscle. Within single-unit muscle, the whole bundle or sheet of smooth muscle cells contracts as a syncytium. Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder and uterus. In the walls of blood vessels, and lymph vessels, (excluding blood and lymph capillaries) it is known as vascular smooth muscle. There is smooth muscle in the tracts of the respiratory, urinary, and reproductive systems. In the eyes, the ciliary muscles, iris dilator muscle, and iris sphincter muscle are types of smooth muscles. The iris dilator and s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Insulin
Insulin (, from Latin ''insula'', 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (''INS)'' gene. It is the main Anabolism, anabolic hormone of the body. It regulates the metabolism of carbohydrates, fats, and protein by promoting the absorption of glucose from the blood into cells of the liver, fat cell, fat, and skeletal muscles. In these tissues the absorbed glucose is converted into either glycogen, via glycogenesis, or Fatty acid metabolism#Glycolytic end products are used in the conversion of carbohydrates into fatty acids, fats (triglycerides), via lipogenesis; in the liver, glucose is converted into both. Glucose production and secretion by the liver are strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a wide variety of tissues. It is thus an anabolic hormone, promoting the conversion of small molecules in the blood into large ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neurotransmitter
A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a Chemical synapse, synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. Some neurotransmitters are also stored in large dense core vesicles. The neurotransmitter's effect on the target cell is determined by the receptor it binds to. Many neurotransmitters are synthesized from simple and plentiful precursors such as amino acids, which are readily available and often require a small number of biosynthetic steps for conversion. Neurotransmitters are essential to the function of complex neural systems. The exact number of unique neurotransmitters in humans is unknown, but more than 100 have been identified. Common neurotransmitters include Glutamate (neurotransmi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BK Channel
BK channels (big potassium), are large conductance calcium-activated potassium channels, and is also known as BKCa, Maxi-K, slo1, or Kca1.1. BK channels are voltage-gated potassium channels that conduct large amounts of potassium ions (K+) across the cell membrane, hence their name, ''big potassium''. These channels can be activated (opened) by either electrical means, or by increasing Ca2+ concentrations in the cell. BK channels help regulate physiological processes, such as circadian behavioral rhythms and neuronal excitability. BK channels are also involved in many processes in the body, as it is a ubiquitous channel. They have a tetrameric structure that is composed of a transmembrane domain, voltage sensing domain, potassium channel domain, and a cytoplasmic C-terminal domain, with many X-ray structures for reference. Their function is to repolarize the membrane potential by allowing for potassium to flow outward, in response to a depolarization or increase in calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lysine
Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. Lysine contains an α-amino group (which is in the protonated form when the lysine is dissolved in water at physiological pH), an α-carboxylic acid group (which is in the deprotonated form when the lysine is dissolved in water at physiological pH), and a side chain (which is partially protonated when the lysine is dissolved in water at physiological pH), and so it is classified as a basic, charged (in water at physiological pH), aliphatic amino acid. It is encoded by the codons AAA and AAG. Like almost all other amino acids, the α-carbon is chiral and lysine may refer to either enantiomer or a racemic mixture of both. For the purpose of this article, lysine will refer to the biologically active enantiomer L-lysine, where the α-carbon is in the ''S'' configuration. The human body cannot synthesize lysine. It is essential in humans and must therefore be obtained from the diet. In orga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iberiotoxin
Iberiotoxin (IbTX) is an ion channel toxin purified from the Eastern Indian red scorpion ''Hottentotta tamulus''. Iberiotoxin selectively inhibits the current through large-conductance calcium-activated potassium channels. Chemistry Iberiotoxin is a 37-amino acid peptide. The formula is C179H274N50O55S7. It is also known as "Potassium channel toxin alpha-KTx 1.3" or IbTx. The complete amino acid sequence has been defined and it displays 68% sequence homology with charybdotoxin. Target and mode of action Iberiotoxin binds to the outer face of the large-conductance calcium-activated potassium channels (maxiK or BK channels) with high affinity (Kd ~1 nM). It selectively inhibits the current by decreasing both the probability of opening and the open time of the channel. Toxicity The venom produces mainly cardiopulmonary abnormalities like circulatory derangements, myocarditis and changes in cardiac sarcolemmal ATPase and by these abnormalities it can finally cause death. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calcium-activated Potassium Channel
Calcium-activated potassium channels are potassium channels gated by calcium, or that are structurally or phylogenetically related to calcium gated channels. They were first discovered in 1958 by Gardos who saw that calcium levels inside of a cell could affect the permeability of potassium through that cell membrane. Then in 1970, Meech was the first to observe that intracellular calcium could trigger potassium currents. In humans they are divided into three subtypes: BK channel, large conductance or BK channels, which have very high conductance which range from 100 to 300 pS, intermediate conductance or IK channels, with intermediate conductance ranging from 25 to 100 pS, and small conductance or SK channels with small conductances from 2-25 pS. This family of ion channels is, for the most part, activated by intracellular Ca2+ and contains 8 members in the human genome. However, some of these channels (the KCa4 and KCa5 channels) are responsive instead to other intracellular ligan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
