Vacuolar-type ATPase (V-ATPase) is a highly conserved evolutionarily ancient enzyme with remarkably diverse functions in eukaryotic organisms.[1] V-ATPases acidify a wide array of intracellular organelles and pump protons across the plasma membranes of numerous cell types. V-ATPases couple the energy of ATP hydrolysis to proton transport across intracellular and plasma membranes of eukaryotic cells. It is generally seen as the polar opposite of ATP synthase because ATP synthase is a proton channel that uses the energy from a proton gradient to produce ATP. V-ATPase however, is a proton pump that uses the energy from ATP hydrolysis to produce a proton gradient.
The Archaea-type ATPase (A-ATPase) is a related group of ATPases found in Archaea that often work as an ATP synthase. It forms a clade V/A-ATPase with V-ATPase. Most members of either group shuttle protons (H+
), but a few members have evolved to use sodium ions (Na+
) instead.
Subunit d/C[edit]
Subunit d in V-ATPases, called subunit C in A-ATpases, is a part of the Vo complex. They fit onto the middle of the c ring, so are thought to function as a rotor. There are two versions of this subunit in eukaryotes, d/d1 and d2.[25]
In mammals, d1 (ATP6V0D1) is the ubiquitously expressed version and d2 (ATP6V0D2) is expressed in specific cell types only.[25]
Subunit a/I[edit]
The 116kDa subunit (or subunit a) and subunit I are found in the Vo or Ao complex of V- or A-ATPases, respectively. The 116kDa subunit is a transmembrane glycoprotein required for the assembly and proton transport activity of the ATPase complex. Several isoforms of the 116kDa subunit exist, providing a potential role in the differential targeting and regulation of the V-ATPase for specific organelles.
The function of the 116-kDa subunit is not defined, but its predicted structure consists of 6–8 transmembranous sectors, suggesting that it may function similar to subunit a of FO.
A relatively new technique called ancestral gene resurrection has shed new light on the evolutionary history of the V-ATPase. It has been shown how the V-ATPase structure of the ancestral form consisting of two different proteins evolves into the fungi version with three different proteins.[33][34][35] The V-Type ATPase is similar to the archaeal (so called) A-Type ATP synthase, a fact that supports an archaeal origin of eukaryotes (like Eocyte Hypothesis, see also Lokiarchaeota). The exceptional occurrence of some lineages of archaea with F-type and of some lineages of bacteria with A-type ATPase respectively is regarded as a result of horizontal gene transfer.[36]
Disassembly and reassembly of V-ATPases does not require new protein synthesis but does need an intact microtubular network.[39]
One gene is carbonic anhydrase II (CAII), which, when mutated, causes osteopetrosis with renal tubular acidosis(type 3).[44]
The disease has a childhood onset and results in a slowly progressive muscle weakness, typically beginning in the legs, and some patients can eventually require wheelchair assistance with advanced age. The Vma21 protein assists in assembly of the V-ATPase, and XMEA associated mutations result in decreased activity of the V-ATPase and increased lysosomal pH.[53]
The term Vo has a lowercase letter "o" (not the number "zero") in subscript. The "o" stands for oligomycin, which binds to the homologous region in F-ATPase. It is worth noting that the human gene notations at NCBI designate it as "zero" rather than the letter "o". For example, the gene for the human c subunit of Vo is listed in NCBI gene database as "ATP6V0C" (with a zero), rather than "ATP6VOC" (with an "o"). Many pieces of literature make this mistake as well.
https://en.wikipedia.org/wiki/V-ATPase
Missy Elliott - Get Ur Freak On [Official Music Video]
Flippases (rarely spelled flipases) are transmembrane lipid transporter proteins located in the membrane which belong to ABC transporter or P4-type ATPase families. They are responsible for aiding the movement of phospholipid molecules between the two leaflets that compose a cell's membrane (transverse diffusion, also known as a "flip-flop" transition). The possibility of active maintenance of an asymmetric distribution of molecules in the phospholipid bilayer was predicted in the early 1970s by Mark Bretscher.[2][3] Although phospholipids diffuse rapidly in the plane of the membrane, their polar head groups cannot pass easily through the hydrophobic center of the bilayer, limiting their diffusion in this dimension. Some flippases - often instead called scramblases[1] - are energy-independent and bidirectional, causing reversible equilibration of phospholipid between the two sides of the membrane, whereas others are energy-dependent and unidirectional, using energy from ATP hydrolysis to pump the phospholipid in a preferred direction.[4] Flippases are described as transporters that move lipids from the exoplasmic to the cytosolic face, while floppases transport in the reverse direction.[1]
Many cells maintain asymmetric distributions of phospholipids between their cytoplasmic and exoplasmic membrane leaflets.[5] The loss of asymmetry, in particular the appearance of the anionic phospholipid phosphatidylserine on the exoplasmic face, can serve as an early indicator of apoptosis[6] and as a signal for efferocytosis.[7]
https://en.wikipedia.org/wiki/Flippase
Scramblase is a protein responsible for the translocation of phospholipids between the two monolayers of a lipid bilayer of a cell membrane.[1][2][3] In humans, phospholipid scramblases (PLSCRs) constitute a family of five homologous proteins that are named as hPLSCR1–hPLSCR5. Scramblases are not members of the general family of transmembrane lipid transporters known as flippases. Scramblases are distinct from flippases and floppases. Scramblases, flippases, and floppases are three different types of enzymatic groups of phospholipid transportation enzymes.[4] The inner-leaflet, facing the inside of the cell, contains negatively charged amino-phospholipids and phosphatidylethanolamine. The outer-leaflet, facing the outside environment, contains phosphatidylcholine and sphingomyelin. Scramblase is an enzyme, present in the cell membrane, that can transport (scramble) the negatively charged phospholipids from the inner-leaflet to the outer-leaflet, and vice versa.
https://en.wikipedia.org/wiki/Phospholipid_scramblase
Phosphatidylethanolamine (PE) is a class of phospholipids found in biological membranes.[1] They are synthesized by the addition of cytidine diphosphate-ethanolamine to diglycerides, releasing cytidine monophosphate. S-Adenosyl methionine can subsequently methylate the amine of phosphatidylethanolamines to yield phosphatidylcholines. It can mainly be found in the inner (cytoplasmic) leaflet of the lipid bilayer.[2]
Phosphatidylethanolamines are found in all living cells, composing 25% of all phospholipids. In human physiology, they are found particularly in nervous tissue such as the white matter of brain, nerves, neural tissue, and in spinal cord, where they make up 45% of all phospholipids.[3]
Phosphatidylethanolamines play a role in membrane fusion and in disassembly of the contractile ring during cytokinesis in cell division.[4] Additionally, it is thought that phosphatidylethanolamine regulates membrane curvature. Phosphatidylethanolamine is an important precursor, substrate, or donor in several biological pathways.[3]
As a polar head group, phosphatidylethanolamine creates a more viscous lipid membrane compared to phosphatidylcholine. For example, the melting temperature of di-oleoyl-phosphatidylethanolamine is -16 °C while the melting temperature of di-oleoyl-phosphatidylcholine is -20 °C. If the lipids had two palmitoyl chains, phosphatidylethanolamine would melt at 63 °C while phosphatidylcholine would melt already at 41 °C.[5]Lower melting temperatures correspond, in a simplistic view, to more fluid membranes.
https://en.wikipedia.org/wiki/Phosphatidylethanolamine
08-29-2021-214 - Vacuolar-type ATPase (V-ATPase) Archaea-type ATPase (A-ATPase) clade V/A-ATPase V-ATPase archaea vacuoles vacuolar ancient ATP6V0D2 d2 d1 d ATP P horizontal pump proton synthase acid intracellular transport plasma eukaryote cell energy proton gradient Na sodium Vo rotor rotary mechanics mechanical ubiquitously expressed version the a of seven glycoprotein protein transmembrane receptor gen mod gen-mod christ 9 Most members of either group shuttle protons (H+ ), but a few members have evolved to use sodium ions (Na+ ) instead. fungus Phosphatidylethanolamine sharon petersen genetic disease diglyceride fusion fission binary contractile ring dysfunction polar head viscous viscosity increase blood thickening choline oleoyl palmitoylization palmitoyl fluid ethanolamine phospholipid dysfunction x-linked disease cytoplasmi viscos inc cytidine phosphate + genetic disease = glycerolization/glycolation/proteinization/lipification/palmivation/sterolization/hormone radical/etc. lipodystrophy = HIV +
08-29-2021-214 - Vacuolar-type ATPase (V-ATPase) Archaea-type ATPase (A-ATPase) clade V/A-ATPase V-ATPase archaea vacuoles vacuolar ancient ATP6V0D2 d2 d1 d ATP P horizontal pump proton synthase acid intracellular transport plasma eukaryote cell energy proton gradient Na sodium Vo rotor rotary mechanics mechanical ubiquitously expressed version the a of seven glycoprotein protein transmembrane receptor gen mod gen-mod christ 9 Most members of either group shuttle protons (H+ ), but a few members have evolved to use sodium ions (Na+ ) instead. fungus Phosphatidylethanolamine sharon petersen genetic disease diglyceride fusion fission binary contractile ring dysfunction polar head viscous viscosity increase blood thickening choline oleoyl palmitoylization palmitoyl fluid ethanolamine phospholipid dysfunction x-linked disease cytoplasmi viscos inc cytidine phosphate + genetic disease = glycerolization/glycolation/proteinization/lipification/palmivation/sterolization/hormone radical/etc. lipodystrophy = HIV + neander gene test resurrection proteobactre Proteobacteria gram negative sensitivity sensitive to phosphate phosphoric acid phosphorus agony marajiuana alkali environment preferred by HIV+; HIV N/A is acid in global environment of increasingly HIV+ with alkalization of environment and addition of anti-neoplasics alkai methroxetrate to crop/viand stabilizstion/etc.
No comments:
Post a Comment