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Parabutoxin
Parabutoxin (PBTx) is a Shaker gene, Shaker-related voltage-gated K+ channel, voltage-gated K+ channel (Kvα1) inhibitor purified from different ''Parabuthus'' scorpion species found in southern Africa. It occurs in different forms: parabutoxin 1 (PBTx1), parabutoxin 2 (PBTx2), parabutoxin 3 (PBTx3) and parabutoxin (PBTx10). The different variants have different affinities towards Kvα1 channels. Sources Four different acidic peptides (PBTx1, PBTx2, PBTx3 and PBTx10) have been isolated and cloned from the venoms of three different ''Parabuthus'' scorpion species found in southern Africa. PBTx1 and PBTx3 were extracted from the venom of ''Parabuthus transvaalicus, P. transvaalicus'', PBTx2 from ''Parabuthus villosus, P. villosus'' and PBTx10 has been purified from ''P. granulatus''. Chemistry Scorpion toxins that target potassium channels have been classified into three K+ Toxin (KT) subfamilies α-KTx, β-KTx, and γ-KTx peptides. The α-KTx subfamilies are the best-studied tox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabuthus
''Parabuthus'', commonly known as the thick-tailed scorpion, is a genus of large and highly venomous Afrotropical realm, Afrotropical scorpions, that show a preference for areas of low rainfall. Their stings are medically important and human fatalities have been recorded.Larsen, Norman. Biodiversity Explorer, IZIKO. Scorpion stings and venom/ref> Characteristics They have thick and strong tails, with typically a rough surface to the first (proximal) and sometimes second segment, that is used to produce a warning sound when rubbed against the sting (save ''Parabuthus distridor, P. distridor''). Their thick tails are also employed in excavating their shallow burrows, as several are adapted to sandy environments. Some flatter-bodied species, however, take refuge in rock crevasses. Due to their stings' quick-acting venom, they rely to lesser extent on their slender pinchers (chelae) to hold onto prey. Three species, ''Parabuthus schlechteri, P. schlechteri'', ''Parabuthus transvaalic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shaker Gene
The ''shaker (Sh)'' gene, when mutated, causes a variety of atypical behaviors in the fruit fly, ''Drosophila melanogaster''. Under ether anesthesia, the fly’s legs will shake (hence the name); even when the fly is unanaesthetized, it will exhibit aberrant movements. Sh-mutant flies have a shorter lifespan than regular flies; in their larvae, the repetitive firing of action potentials as well as prolonged exposure to neurotransmitters at neuromuscular junctions occurs. In ''Drosophila'', the shaker gene is located on the X chromosome. The closest human homolog is KCNA3. Function The ''Sh'' gene plays a part in the operation of potassium ion channels, which are integral membrane proteins and are essential to the correct functioning of the cell. A working shaker channel is voltage-dependent and has four subunits, which form a pore through which ions flow, carrying type-A potassium current (IA). A mutation in the Sh gene reduces the conductance of charge across the neuron ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage-gated K+ Channel
Voltage-gated potassium channels (VGKCs) are transmembrane channels specific for potassium and 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-related: Kv1.1 ( KCNA1), Kv1.2 (KCNA2), Kv1.3 (KCNA3), Kv1.5 (KCNA5), Kv1.6 (KCNA6), Kv1.7 ( KCNA7), Kv1.8 ( KCNA10) *Kvα2.x - Shab-related: Kv2.1 ( KCNB1), Kv2.2 ( KCNB2) *Kvα3 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Southern Africa
Southern Africa is the southernmost region of Africa. No definition is agreed upon, but some groupings include the United Nations geoscheme for Africa, United Nations geoscheme, the intergovernmental Southern African Development Community, and the #Definitions and Usage, physical geography definition based on the physical characteristics of the land. The most restrictive definition considers the region of Southern Africa to consist of Botswana, Eswatini, Lesotho, Namibia, and South Africa, while other definitions also include several other countries from the area. Defined by physical geography, Southern Africa is home to several river systems; the Zambezi, Zambezi River is the most prominent. The Zambezi flows from the northwest corner of Zambia and western Angola to the Indian Ocean on the coast of Mozambique. Along the way, it flows over Victoria Falls on the border between Zambia and Zimbabwe. Victoria Falls is one of the largest waterfalls in the world and a major tourist a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabuthus Transvaalicus
''Parabuthus transvaalicus'' (known as the Transvaalicus thick-tailed scorpion, South African thick tail, or giant deathstalker) is a species of venomous scorpion from semi-arid parts of southern Africa. Description ''Parabuthus transvaalicus'' grows to a length of , and is dark brown or black in colour, so it is also known as the Black Thick-Tailed scorpion. Its pincers are thin, but its tail is thickened, with the sting segment being as wide as the rest of the tail. It is nocturnal, resting in a shallow burrow under rocks during the day. It resembles its congener '' P. villosus'', which is less strictly nocturnal, hairier and has a more westerly distribution. Distribution ''Parabuthus transvaalicus'' is found in deserts, scrublands and semi-arid regions of Botswana, Mozambique, Zimbabwe, some parts of the Namib Desert and South Africa. Sting ''Parabuthus transvaalicus'' is a dangerous, medically significant scorpion, which can both sting and spray its kurtoxin venom. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Parabuthus Villosus
''Parabuthus villosus'', the black hairy thick-tailed scorpion, is a species of scorpion from southern Africa, where it ranges from the Northern Cape to Namibia. It is the largest species of the Buthidae, measuring up to 18 cm, and its diet may include lizards and mice. The species is often active at dawn and dusk, but takes refuge by day in a variety of shelters. It resembles ''Parabuthus transvaalicus ''Parabuthus transvaalicus'' (known as the Transvaalicus thick-tailed scorpion, South African thick tail, or giant deathstalker) is a species of venomous scorpion from semi-arid parts of southern Africa. Description ''Parabuthus transvaalicus'' ...'', which is more strictly nocturnal, less hairy and with a more easterly distribution. References villosus Arachnids of Africa Animals described in 1862 Taxa named by Wilhelm Peters {{Scorpion-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isoelectric Point
The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electric charge, electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). However, pI is also used. For concision, brevity, this article uses pI. The net charge on the molecule is affected by pH of its surrounding environment and can become more positively or negatively charged due to the gain or loss, respectively, of protons#In Physics and biochemistry, protons (H+). Surfaces naturally charge to form a double layer (interfacial), double layer. In the common case when the surface charge-determining ions are H+/HO−, the net surface charge is affected by the pH of the liquid in which the solid is submerged. The pI value can affect the solubility of a molecule at a given pH. Such molecules have minimum solubility in water or salt solutions at the pH that corresponds to their pI and often precipitate out of Solutio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrophobic Effect
The hydrophobic effect is the observed tendency of nonpolar substances to aggregate in an aqueous solution and to be excluded by water. The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. A positive free energy change of the surrounding solvent indicates hydrophobicity, whereas a negative free energy change implies hydrophilicity. The hydrophobic effect is responsible for the separation of a mixture of oil and water into its two components. It is also responsible for effects related to biology, including: cell membrane and vesicle formation, protein folding, insertion of membrane proteins into the nonpolar lipid environment and protein-small molecule associations. Hence the hydrophobic effect i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Disulfide Bond
In chemistry, a disulfide (or disulphide in British English) is a compound containing a functional group or the anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups. In inorganic chemistry, the anion appears in a few rare minerals, but the functional group has tremendous importance in biochemistry. Disulfide bridges formed between thiol groups in two cysteine residues are an important component of the tertiary and quaternary structure of proteins. Compounds of the form are usually called '' persulfides'' instead. Organic disulfides Structure Disulfides have a C–S–S–C dihedral angle approaching 90°. The S–S bond length is 2.03 Å in diphenyl disulfide, similar to that in elemental sulfur. Disulfides are usually symmetric but they can also be unsymmetric. Symmetrical disulfides are compounds of the formula . Most disulfides encountered in organosulfur chemistry are symmetrical disulfides. Unsy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KCNA2
Potassium voltage-gated channel subfamily A member 2 also known as Kv1.2 is a protein that in humans is encoded by the ''KCNA2'' gene. Function Potassium channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume. Four sequence-related potassium channel genes - shaker, shaw, shab, and shal - have been identified in Drosophila, and each has been shown to have human homolog(s). This gene encodes a member of the potassium channel, voltage-gated, shaker-related subfamily. This member contains six membrane-spanning domains with a shaker-type repeat in the fourth segment. It belongs to the delayed rectifier class, members of which allow nerve cells to efficiently repolarize following an action potential. The coding region of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
KCNA3
Potassium voltage-gated channel, shaker-related subfamily, member 3, also known as KCNA3 or Kv1.3, is a protein that in humans is encoded by the ''KCNA3'' gene. Potassium channels represent the most complex class of voltage-gated ion channels from both functional and structural standpoints. Their diverse functions include regulating neurotransmitter release, heart rate, insulin secretion, neuronal excitability, epithelial electrolyte transport, smooth muscle contraction, and cell volume. Four sequence-related potassium channel genes – shaker, shaw, shab, and shal – have been identified in Drosophila, and each has been shown to have human homolog(s). This gene encodes a member of the potassium channel, voltage-gated, shaker gene, shaker-related subfamily. This member contains six membrane-spanning domains with a shaker-type repeat in the fourth segment. It belongs to the Voltage-gated potassium channel#Delayed rectifier, delayed rectifier class, members of which allow nerve c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissociation Constant
In chemistry, biochemistry, and pharmacology, a dissociation constant (''K''D) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions. The dissociation constant is the inverse of the association constant. In the special case of salts, the dissociation constant can also be called an ionization constant. For a general reaction: : A_\mathit B_\mathit \mathit A + \mathit B in which a complex \ce_x \ce_y breaks down into ''x'' A subunits and ''y'' B subunits, the dissociation constant is defined as : K_\mathrm = \frac where and ''x'' B''y''are the equilibrium concentrations of A, B, and the complex A''x'' B''y'', respectively. One reason for the popularity of the dissociation constant in biochemistry and pharmacology is that in the frequen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
