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AaTX1
AaTX1 is a scorpion toxin of the α-KTx15 subfamily originally found in the venom of ''Androctonus australis.'' The toxin acts as a specific blocker on Kv4.3 voltage-gated potassium channel, thereby abolishing the A-type potassium currents. Etymology and source AaTX1 is a peptide that can be purified from the venom of ''Androctonus australis''. ''Androctonus australis'' is a fat-tailed desert scorpion distributed over North Africa and the Middle East. AaTX1 represents only 0.007% ( w/v) of ''Androctonus australis'' venom. Chemistry The peptide consists of 37 amino acid residues, which include six cysteines. These cysteines form disulfide bridges, cross-linking the residues along the peptidyl chain. The determined molecular mass of the peptide appears to be approximately 3851 Da. AaTX1 is a member of the α-KTx15 subfamily (α-KTx15-4). This family consists of six peptides, which share high level of sequence similarity: Aa1, AaTX1, AaTX2, AmmTX3, BmTX3 and Discrepin. More ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AmmTX3
AmmTX3, produced by ''Androctonus mauretanicus'', is a scorpion toxin of the α-KTX15 subfamily. The toxin is known for its ability to act as a specific Kv4 channel blocker, and thereby reducing the A-type potassium current through this channel. Etymology and source AmmTX3 (α-KTX15.3) is a peptide that can be isolated from the venom of ''Androctonus mauretanicus''. ''Androctonus mauretanicus'' is a fat-tailed scorpion with its origins in North Africa. Chemistry AmmTX3 has a molecular mass of 3823.5 Da and consists of a single chain of 37 amino acid residues. These residues are cross-linked by three disulfide bridges. The toxin contains the dyad characteristic (K27 and Y36) that is found in pore-blocking potassium channel-specific toxins, and is therefore likely to act as a pore blocker. AmmTX3 is a member of the α-KTX15 subfamily. This subfamily currently exists of six very homologous peptides, originating from scorpion venom: Aa1, AaTX1, AaTX2, AmmTX3, BmTx3 and Discr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Androctonus Australis
''Androctonus australis'', the yellow fat-tailed scorpion, is a hardy desert scorpion from North Africa, Somaliland, the Middle East, Pakistan and India. ''A. australis'', along with '' A. amoreuxi'' and '' Pandinus imperator'', is the most commonly available scorpions found in the exotic animal trade. Hardiness Unlike most other animals that live in deserts, ''Androctonus'' does not dig burrows to protect itself from a sandstorm. Instead, it can withstand sandstorms powerful enough to strip paint off steel, without any apparent damage. The resistance of ''Androctonus'' to sandstorms is suspected to be due to its unusual exoskeleton surface texture. Its armor is covered with dome-shaped granules that are high and across. When this surface texture is translated into other materials it protects them to a certain degree as well, which has led to the possibility of the applicability of imitation surfaces in such objects as aeroplanes and helicopters. Etymology The name ''And ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scorpion Toxin
Scorpion toxins are proteins found in the venom of scorpions. Their toxic effect may be mammal- or insect-specific and acts by binding with varying degrees of specificity to members of the Voltage-gated ion channel superfamily; specifically, voltage-gated sodium channels, voltage-gated potassium channels, and Transient Receptor Potential (TRP) channels. The result of this action is to activate or inhibit the action of these channels in the nervous and cardiac organ systems. For instance, α-scorpion toxins MeuNaTxα-12 and MeuNaTxα-13 from ''Mesobuthus eupeus'' are neurotoxins that target voltage-gated Na+ channels (Navs), inhibiting fast inactivation. ''In vivo'' assays of MeuNaTxα-12 and MeuNaTxα-13 effects on mammalian and insect Navs show differential potency. These recombinants (MeuNaTxα-12 and MeuNaTxα-13) exhibit their preferential affinity for mammalian and insect Na+ channels at the α-like toxins' active site, site 3, in order to inactivate the cell membrane depolari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disulfide
In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In biology, disulfide bridges formed between thiol groups in two cysteine residues are an important component of the secondary and tertiary structure of proteins. ''Persulfide'' usually refers to compounds. In inorganic chemistry disulfide usually refers to the corresponding anion (−S−S−). Organic disulfides Symmetrical disulfides are compounds of the formula . Most disulfides encountered in organo sulfur chemistry are symmetrical disulfides. Unsymmetrical disulfides (also called heterodisulfides) are compounds of the formula . They are less common in organic chemistry, but most disulfides in nature are unsymmetrical. Properties The disulfide bonds are strong, with a typical bond dissociation energy of 60 kcal/mol (251&nbs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dopamine
Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic compound, organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 80% of the catecholamine content in the brain. It is an amine synthesized by removing a carboxyl group from a molecule of its precursor (chemistry), precursor chemical, L-DOPA, which is biosynthesis, synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons (nerve cells) to send signals to other nerve cells. Neurotransmitters are synthesized in specific regions of the brain, but affect many regions systemically. The brain includes several distinct dopaminergic pathway, dopamine pathways, one of which plays a major role in the motivational component of reward system, reward-motivated behavior. The anticipa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpha Helix
The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues earlier along the protein sequence. The alpha helix is also called a classic Pauling–Corey–Branson α-helix. The name 3.613-helix is also used for this type of helix, denoting the average number of residues per helical turn, with 13 atoms being involved in the ring formed by the hydrogen bond. Among types of local structure in proteins, the α-helix is the most extreme and the most predictable from sequence, as well as the most prevalent. Discovery In the early 1930s, William Astbury showed that there were drastic changes in the X-ray fiber diffraction of moist wool or hair fibers upon significant stretching. The data suggested that the unstretched fibers had a coiled molecular structure with a characteristic repeat of ≈. Astb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Beta Sheet
The beta sheet, (β-sheet) (also β-pleated sheet) is a common motif of the regular protein secondary structure. Beta sheets consist of beta strands (β-strands) connected laterally by at least two or three backbone hydrogen bonds, forming a generally twisted, pleated sheet. A β-strand is a stretch of polypeptide chain typically 3 to 10 amino acids long with backbone in an extended conformation. The supramolecular association of β-sheets has been implicated in the formation of the fibrils and protein aggregates observed in amyloidosis, notably Alzheimer's disease. History The first β-sheet structure was proposed by William Astbury in the 1930s. He proposed the idea of hydrogen bonding between the peptide bonds of parallel or antiparallel extended β-strands. However, Astbury did not have the necessary data on the bond geometry of the amino acids in order to build accurate models, especially since he did not then know that the peptide bond was planar. A refined versi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Antiparallel (biochemistry)
In biochemistry, two biopolymers are antiparallel if they run parallel to each other but with opposite directionality (alignments). An example is the two complementary strands of a DNA double helix, which run in opposite directions alongside each other. Nucleic acids Nucleic acid molecules have a phosphoryl (5') end and a hydroxyl (3') end. This notation follows from organic chemistry nomenclature, and can be used to define the movement of enzymes such as DNA polymerases relative to the DNA strand in a non-arbitrary manner. G-quadruplexes G-quadruplexes, also known as G4 DNA are secondary structures found in nucleic acids that are rich in guanine. These structures are normally located at the telomeres (the ends of the chromosomes). The G-quadruplex can either be parallel or antiparallel depending on the loop configuration, which is a component of the structure. If all the DNA strands run in the same direction, it is termed to be a parallel quadruplex, and is known as a str ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Potassium Channel
Potassium channels are the most widely distributed type of ion channel found in virtually all organisms. They form potassium-selective pores that span cell membranes. Potassium channels are found in most cell types and control a wide variety of cell functions. Function Potassium channels function to conduct potassium ions down their electrochemical gradient, doing so both rapidly (up to the diffusion rate of K+ ions in bulk water) and selectively (excluding, most notably, sodium despite the sub-angstrom difference in ionic radius). Biologically, these channels act to set or reset the resting potential in many cells. In excitable cells, such as neurons, the delayed counterflow of potassium ions shapes the action potential. By contributing to the regulation of the cardiac action potential duration in cardiac muscle, malfunction of potassium channels may cause life-threatening arrhythmias. Potassium channels may also be involved in maintaining vascular tone. They also regulate ce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Discrepin
Discrepin (α-KTx15.6) is a peptide from the venom of the Venezuelan scorpion ''Tityus discrepans''. It acts as a neurotoxin by irreversibly blocking A-type voltage-dependent K+-channels. Etymology and source Discrepin is named after its source: a Venezuelan scorpion called ''Tityus discrepans''. Its systematic number is α-KTx15.6. Chemistry The subfamily α-KTx15 consists of 6 toxins. The first five toxins of this subfamily are very much alike, but discrepin only shares 50% amino acid homology with other members of this subfamily. Discrepin contains 38 amino acid residues. It has a polyglutamic acid at its N-terminal region. Discrepin has the α and β folds that are characteristic of scorpion toxins. It consists of one α-helix and three β-sheet helix strands. The α-helix is formed from amino acid Ser11 until Arg21. The three antiparallel β-sheets are formed from amino acid Ile2 until Lys7, Ala27 until Cys29 and Arg33 until Cys36. Target Discrepin blocks voltage-gated Sh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BmTx3
BmTx3 is a neurotoxin, which is a component of the venom of the scorpion ''Buthus Martensi'' Karsch. It blocks A-type potassium channels in the central nervous system and hERG-channels in the heart. Source/Isolation BmTx3 was originally purified from the venom of the Chinese scorpion, ''Buthus Martensi'' Karsch. BmTx3 is a “short-chain” peptide like other potassium channel blockers in the scorpion venom and added to the phylogenetic tree in the subfamily α-KTx15. Its 3D structure has not yet been elucidated, but based on sequence similarity it likely resembles the 3D structure of BmTx1 or Discrepin. Biochemistry BmTx3 consists of an α-helix and two β-sheet segments cross-linked by three disulfide bridges (Cs-α/β motif). It is a short chain peptide with a molecular mass of 3751.6 Da; it consists of 37 amino acids. Target BmTx3 is the first toxin from the scorpion α-KTx subfamily 15 with two functional faces. As all α-KTx peptides, BmTx3 blocks A-type (IA) potassium ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Mass
The molecular mass (''m'') is the mass of a given molecule: it is measured in daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The related quantity relative molecular mass, as defined by IUPAC, is the ratio of the mass of a molecule to the unified atomic mass unit (also known as the dalton) and is unitless. The molecular mass and relative molecular mass are distinct from but related to the molar mass. The molar mass is defined as the mass of a given substance divided by the amount of a substance and is expressed in g/mol. That makes the molar mass an average of many particles or molecules, and the molecular mass the mass of one specific particle or molecule. The molar mass is usually the more appropriate figure when dealing with macroscopic (weigh-able) quantities of a substance. The definition of molecular weight is most authoritatively synonymous with relative molecular mass; ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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